JP2013175756A - Magnetic storage element, magnetic storage device and magnetic memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic storage element, a magnetic storage device and a magnetic memory that can stably perform movement of domain walls while being capable of reducing current density required for causing the domain walls to be subjected to transition from standstill states to moving states.SOLUTION: A magnetic storage element 1 comprises: a magnetic thin wire 100 that extends in a first direction and has a plurality of domains 101through 101separated by domain walls; electrodes 104a and 104b capable of causing a current to flow through the magnetic thin wire 100 in the first direction or in a direction opposite to the first direction; and an assist section that receives an electrical input and assists movement of the domain walls of all regions or a part thereof of the magnetic thin wire 100. The assist section comprises: a magnetic layer disposed adjacent to at least the part of the regions of the magnetic thin wire 100; and wiring 230 for applying a current magnetic field generated by the current flowing to the magnetic layer.

Description

  Embodiments described herein relate generally to a magnetic storage element, a magnetic storage device, and a magnetic memory.

  As a method for realizing a large memory capacity, a spin shift register type memory using a domain wall has been proposed. This is not a method of creating “storage element + selection element + information lead-out wiring” in each memory cell, which has been continued in the conventional semiconductor memory, but a sensor and a wiring in which stored information is formed in a fixed place. This method is based on the concept of arranging only the memory elements at a high density by using the method of transferring the data to the position, and may greatly increase the memory capacity.

  However, in order to realize a stable shift operation, a current having a large current density is required to shift the domain wall from a stationary state to a moving state. The need for high current and high power for frequent shift operations is an undesirable configuration from the two viewpoints of ensuring reliability and power consumption as a memory, and reducing the critical current value required for domain wall shift operations. It is necessary to make it.

  In addition, it is not desirable for a shift register for memory to have a control electrode attached to each bit (or each digit), and it is necessary to perform a shift operation of a desired number of digits by applying some action to the entire bit string. In memory shift registers that have been proposed so far, current pulses that flow through the shift register cause at least several hundred bits in one magnetic wire necessary for realizing a large-capacity memory, even if it is several digits long. In order to increase the capacity, it is not easy to shift all digits of information that can be several kbits or more at a time. In the case of such a large-capacity memory with a large number of bits on one thin line, the physical length of the shift register also increases, and the possibility of malfunction increases due to the dullness of the current pulse waveform due to the capacitance and inductance components. The problem of end up being considered.

JP 2009-301699 A

US Pat. No. 6,834,005

  The problem to be solved by the embodiments of the present invention is to reduce the current density necessary for transitioning the domain wall from a stationary state to a moving state, and to reduce the current density of the domain wall stably. It is to provide a storage element, a magnetic storage device, and a magnetic memory.

  The magnetic memory element of this embodiment includes a magnetic wire having a plurality of magnetic domains extending in a first direction and separated by a domain wall, a current in the first direction and a direction opposite to the first direction in the magnetic wire. An electrode through which an electric current can flow, and an assist unit that receives an electrical input and assists the movement of the domain wall in the whole or a part of the magnetic thin wire, and the assist unit includes the magnetic thin wire. A magnetic layer disposed in the vicinity of at least a part of the region; and a wiring for applying a current magnetic field generated when a current flows to the magnetic layer.

1 is a cross-sectional view showing a magnetic memory element according to a first embodiment. Sectional drawing which shows the magnetic memory element by the 1st modification of 1st Embodiment. Sectional drawing which shows the magnetic memory element by the 2nd modification of 1st Embodiment. 6 is a timing chart showing waveforms of a current and a magnetic field applied to the magnetic thin wire of the magnetic memory element of one embodiment. Sectional drawing explaining the writing and reading of the magnetic memory element by 1st Embodiment. Sectional drawing explaining writing and reading of the magnetic memory element by the 1st modification of 1st Embodiment. FIG. 7A to FIG. 7C are views showing time lapses of domain wall widths and magnetization distributions of the first embodiment and the comparative example. 8A to 8C are cross-sectional views showing a method for manufacturing a magnetic memory element according to a first modification of the first embodiment. Sectional drawing which shows the magnetic memory element by 2nd Embodiment. Sectional drawing which shows the magnetic memory element by the 1st modification of 2nd Embodiment. Sectional drawing which shows the magnetic memory element by the 2nd modification of 2nd Embodiment. Sectional drawing which shows the magnetic memory element of 3rd Embodiment. Sectional drawing which shows the magnetic memory element by the 1st modification of 3rd Embodiment. 14A and 14B are plan views of the third embodiment and the first modification viewed from above the substrate. Sectional drawing which shows the magnetic memory element by the 2nd modification of 3rd Embodiment. Sectional drawing which shows the magnetic memory element by the 3rd modification of 3rd Embodiment. Sectional drawing which shows the magnetic memory element by the 4th modification of 3rd Embodiment. Sectional drawing which shows the magnetic memory element by the 5th modification of 3rd Embodiment. Sectional drawing which shows the magnetic memory element by the 6th modification of 3rd Embodiment. Sectional drawing which shows the magnetic memory element by 4th Embodiment. Sectional drawing which shows the magnetic memory element by the 1st modification of 4th Embodiment. 22A and 22B are views for explaining a magnetic memory element according to the fifth embodiment. Sectional drawing which shows the magnetic memory element by the modification of 5th Embodiment. The perspective view which shows the magnetic memory device by 6th Embodiment. The perspective view which shows the magnetic memory device by the modification of 6th Embodiment. The perspective view which shows the magnetic memory provided with two or more magnetic storage devices of 6th Embodiment or its modification. A circuit diagram showing a magnetic memory device of a 7th embodiment. The perspective view which shows the magnetic memory device of 7th Embodiment.

  Embodiments will be described below with reference to the drawings.

(First embodiment)
A magnetic memory element according to the first embodiment is shown in FIG. FIG. 1 is a cross-sectional view of a magnetic memory element 1 according to the first embodiment. The magnetic memory element 1 of this embodiment includes a magnetic wire 100 formed on or not through a nonmagnetic layer (not shown) on a substrate (not shown), and a current connected to the magnetic wire 100 by connecting to the magnetic wire 100. Electrodes 104 a, 104 b that flow through and wiring 210. The magnetic wire 100 has a thin wire shape extending in one direction. In the present specification, the direction in which the fine line extends is referred to as a fine line direction (first direction). The cross-sectional shape obtained by cutting the magnetic wire 100 by a plane perpendicular to the wire direction is, for example, a quadrangle, a circle, or an ellipse. The magnetic wire 100 has a plurality of magnetic domains 101 _{1 to} 101 _n (n is an integer) inside. FIG. 1 shows n as 7. A magnetic domain refers to a region having a uniform magnetization direction inside.

  At the boundary between two adjacent magnetic domains, the magnetization direction changes continuously in the direction of the thin line. Such a change region of magnetization is called a domain wall. The domain wall generally has a finite width w determined by the anisotropic energy, exchange stiffness, etc. of the magnetic material. When the magnetic memory element is provided with a writing unit and a reading unit, the magnetization direction of each region having a predetermined length in the direction of the thin wire in the magnetic thin wire 100 is associated with 0 or 1 bit data. Therefore, for example, when data “00011011” is stored in the magnetic memory element, the boundary between the region corresponding to the third bit and the region corresponding to the fourth bit, the region corresponding to the fifth bit, and the sixth bit A domain wall exists at each of the boundary of the corresponding region, the region corresponding to the sixth bit, and the boundary of the region corresponding to the seventh bit. The amount of data stored in one magnetic storage element is, for example, 100 to several thousand bits. In FIG. 1, the magnetization direction of each magnetic domain is perpendicular, but may be parallel. In the present specification, the magnetization direction being perpendicular means that the magnetization direction is perpendicular to the thin line direction. In addition, materials that can be used for the magnetic wire 100 will be described later.

  The current source 150 is connected to the magnetic thin wire 100 via the electrodes 104a and 104b, and current can flow in both directions in the magnetic thin wire 100 in both directions. The wiring 210 is disposed in the vicinity of the magnetic wire 100 and is electrically insulated from the magnetic wire 100. In FIG. 1, the magnetic wire 100 is arranged so that the direction of the wire is perpendicular to the substrate surface (for example, the upper surface of the substrate), but in the first modification shown in FIG. , May be arranged parallel to the substrate surface. Further, a plurality (two in FIG. 2) of wirings 211 and 212 may be provided for one magnetic wire 100 as in the second modification shown in FIG.

  The magnetic memory element 1 of this embodiment is manufactured by a film forming technique and a fine processing technique. Details of the manufacturing method will be described later.

  The magnetic memory element 1 of the present embodiment can move the domain wall in the magnetic wire 100 by a predetermined distance in the direction of the wire using the wiring 210 and the current source 150. The procedure will be described.

First, from time t ₂ to time t ₃ (> t ₂ ), a procedure called an assist procedure for passing a current through the wiring 210 is executed. A current magnetic field having a component orthogonal to the magnetization of the magnetic wire 100 is generated around the wiring 210. When there are a plurality of wirings 210, a current is passed through at least one wiring 210. A partial region (referred to as an excitation region) of the magnetic wire 100 is affected by the current magnetic field, and the magnetization direction fluctuates, and the width of the domain wall included in the excitation region is expanded. Since the interaction between dipoles and the exchange interaction act between the magnetizations in the magnetic wire 100, the fluctuation of the magnetization direction propagates in the magnetic wire 100. Therefore, the width of the domain wall in the magnetic wire 100 not included in the excitation region is also expanded as compared with that before the current magnetic field reaches. The current flowing through the wiring 210 may be a pulse current or an alternating current. In the case of alternating current, it is desirable to have a frequency close to the ferromagnetic resonance frequency of the magnetic material constituting the magnetic wire 100. This is because the susceptibility to the magnetic field increases near the resonance frequency, and fluctuations in the magnetization direction can be generated with a smaller current.

At time t ₁ , a current 155 is passed through the magnetic wire 100 using the current source 150.

As is well known, when a current is passed through the magnetic material, the current is spin-polarized in the magnetization direction. Since the magnetization direction changes spatially at the domain wall position, the spin polarization direction of the current 155 also changes spatially accordingly, and the magnetization receives torque from the current 155 due to the reaction.
If the current value is equal to or greater than the threshold value, the position of the domain wall in the magnetic wire 100 moves in the direction 105 in which electrons flow, that is, the direction 105 opposite to the current 155. When the current 155 is turned off, the domain wall stops moving, and therefore the domain wall travel distance can be controlled by the time during which the current 155 is applied.

  At this time, in the magnetic memory element 1 of the present embodiment, since the torque is applied in a state where the domain wall width is widened, the total amount of magnetization involved in the torque transfer increases. Therefore, the efficiency of domain wall motion is improved as compared with the case where a magnetic field is not generated by the current flowing through the wiring 210. Therefore, it becomes possible to move the domain wall with less current and / or in a shorter time, and the stability of the domain wall movement is remarkably improved as compared with the conventional case. In other words, in the present embodiment, the movement of the domain wall is assisted by passing a current through the wiring 210, and the wiring constitutes an assist unit.

  The above procedure is represented as a timing chart as shown in FIG. The time at which the domain wall starts to move is the time at which the current and the magnetic field are applied simultaneously, and is t1 if t2 ≦ t1, and t2 if t1 ≦ t2. In particular, it is desirable that the time t1 is a time after the time t2 (t2 ≦ t1). In addition, when a current is supplied to a plurality of wirings, it is desirable that the condition of t2 ≦ t1 is satisfied for each of the wirings through which the current flows. In this case, the domain wall is moved from time t1 to the time when the supply of current is stopped, and the domain wall movement time is determined by the time during which the current is supplied. Therefore, the controllability for moving the domain wall by a predetermined distance is excellent. As a current flow method, for example, as shown in FIG. 4B, it is also possible to flow the current 155 as a pulse current divided into a plurality of times. Such a current flow method is effective in controlling the timing at which the moved domain wall is stopped. Further, as described above, when the current magnetic field is an alternating magnetic field, the timing charts are as shown in FIGS. 4C and 4D. FIG. 4C shows a case where the AC amplitude changes, and FIG. 4D shows a case where the AC amplitude is constant. The waveform of the magnetic field shown in FIG. 4C shows the magnetic field accompanying the spin wave generated in the magnetic memory elements of the second to fourth embodiments described later, for example.

  It is desirable that the wiring 210 be disposed at a position close to the input portion of the current 155. In addition, when a plurality of wirings are provided in the magnetic memory element 1 and a current is supplied only to a part of the wirings, it is preferable to select the wiring 210 close to the input portion of the current 155 in the magnetic thin wire 100 and to pass the current. desirable. Here, the input portion of the current 155 in the magnetic wire 100 is defined by the direction in which the current 155 flows. The reason will be described with reference to FIG. 3 as a specific example. When the current 155 flows in the direction shown in the figure, the domain wall moves in the direction opposite to the current 155. Of the wiring 211 and wiring 212 for generating a magnetic field, when a current is supplied only to the wiring 211 arranged at a position close to the input portion of the current 155, the domain wall on the traveling direction side of the domain wall moves in a short time. This is because it is difficult for a plurality of domain walls to catch up and overtake.

Next, writing and reading methods of the magnetic memory element 1 according to the first embodiment and the first modification will be described with reference to FIG. FIG. 5 is a view for explaining the writing and reading methods of the magnetoresistive element 1 according to the first embodiment shown in FIG. The magnetoresistive element 1, one end of a magnetic thin wire 100, i.e. the first electrode 104a is provided in a region to be a magnetic domain 101 _1, magnetic wire 103 is provided at the other end. The magnetic wire 103 is used for writing and reading, and the direction of the wire is orthogonal to the direction of the wire of the magnetic wire 100. The second electrode 104 b of the magnetic memory element 1 is provided at the other end of the magnetic wire 103. By passing a current between the electrodes 104a and 104b, the domain wall of the magnetic wire moves. Further, the magnetic wire 103 is provided with a writing unit 110 and a reading unit 120. In the writing unit 110, an electrode 112a is provided on one surface across the magnetic wire 103, a nonmagnetic layer 114 is provided on the other surface, and a magnetization fixed layer 116 whose magnetization is fixed on the nonmagnetic layer 114 is provided. The electrode 112b is provided on the magnetization fixed layer 116.

  Further, in the reading unit 120, an electrode 122a is provided on one surface across the magnetic wire 103, a nonmagnetic layer 124 is provided on the other surface, and a magnetization fixed layer 126 in which magnetization is fixed on the nonmagnetic layer 124. And the electrode 122b is provided on the magnetization fixed layer 126.

  First, writing will be described. When a current 155 is supplied from the current source 150 between the electrodes 104a and 104b and a current is supplied to the wiring 210, a region where the magnetic thin wire 100 is to be written is between the electrode 112a of the writing unit 110 and the nonmagnetic layer 114. The domain wall is moved to be located at Thereafter, a current is passed between the electrodes 112a and 112b of the writing unit 110, and writing is performed in the region to be written.

  When writing is performed so as to have the magnetization in the same direction as the magnetization direction of the magnetization fixed layer 116, a current is passed from the electrode 112 a to the electrode 112 b through the magnetic thin wire 103, the nonmagnetic layer 114, and the magnetization fixed layer 116. In this case, since electrons flow in the direction opposite to the current, they flow from the electrode 112b to the electrode 112a through the magnetization fixed layer 116, the nonmagnetic layer 114, and the magnetic wire 103. At this time, the electrons that have passed through the magnetization fixed layer 116 are spin-polarized, and the spin-polarized electrons flow through the nonmagnetic layer 114 to the area where the magnetic wire 103 is to be written. Then, spin-polarized electrons having a spin in the same direction as the region to be written pass through the region to be written, but have a spin polarization having a spin opposite to the magnetization direction of the region to be written. The poled electrons exert a spin torque on the magnetization of the region to be written, so that the magnetization direction of the region to be written is directed to the same direction as the magnetization of the magnetization fixed layer 116. Thereby, the magnetization of the region to be written is in the same direction as the magnetization of the magnetization fixed layer 116.

  On the other hand, when writing is performed so that the magnetization direction of the magnetization fixed layer 116 is opposite to the magnetization direction, a current is applied from the electrode 112 b to the electrode 112 a via the magnetization fixed layer 116, the nonmagnetic layer 114, and the magnetic wire 103. Shed. In this case, since electrons flow in the direction opposite to the current, they flow from the electrode 112a to the electrode 112b through the magnetic wire 103, the nonmagnetic layer 114, and the magnetization fixed layer 116. Electrons that have passed through the region to be written on the magnetic wire 103 are spin-polarized, and the spin-polarized electrons flow to the magnetization fixed layer 116 through the nonmagnetic layer 114. Electrons having a spin in the same direction as the magnetization of the magnetization fixed layer 116 pass through the magnetization fixed layer 116, but electrons having a spin in the opposite direction to the magnetization of the magnetization fixed layer 116 are between the nonmagnetic layer 114 and the magnetization fixed layer 116. It is reflected at the interface and flows into the area where the magnetic fine wire layer 103 is to be written. Then, spin-polarized electrons having a spin opposite to the magnetization of the magnetization pinned layer 116 act on the magnetization of the magnetic thin wire 103 in the region to be written, and the magnetization of the region to be written in is applied. It works so that the direction is opposite to the magnetization of the magnetization fixed layer 116. As a result, the magnetization of the region to be written is in the opposite direction to the magnetization of the magnetization fixed layer 116.

  Next, a reading method will be described. When a current 155 is supplied from the current source 150 between the electrodes 104a and 104b and a current is supplied to the wiring 210, a region where the magnetic thin wire 100 is to be read is between the electrode 122a of the reading unit 120 and the nonmagnetic layer 124. The domain wall is moved to be located at Thereafter, a constant current is passed between the electrodes 122a and 122b of the reading unit 120 or a constant voltage is applied. At this time, the reading should be performed using the fact that the electrical resistance between the electrodes 122a and 122b varies depending on the angle formed by the magnetization direction of the region to be read and the magnetization direction of the magnetization fixed layer 126 (magnetoresistance effect). Reads information from the area. Specifically, when the magnetization direction of the region to be read and the magnetization direction of the magnetization fixed layer 126 are parallel (anti-parallel), the resistance value takes a low (high) value.

In the first modification of the first embodiment, the writing method and the reading method are first provided with electrodes 104a and 104b, a writing unit 110, and a reading unit 120 on the magnetic wire 100 as shown in FIG. Do it. That is, in the first embodiment, the writing unit 110 and the reading unit 120 are provided in the magnetic wire 103 connected to the magnetic wire 100. However, in the first modification, the writing unit 110 and the reading unit are provided in the magnetic wire 100. 120 is performed.
The writing method and reading method in the first modification are performed in the same manner as in the first embodiment.

  Next, the material of the magnetic fine wire will be described.

Various magnetic materials can be used for the magnetic wire 100. For example, a magnetic alloy containing at least one element selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), and chromium (Cr) can be used. Typical examples include permalloy (FeNi alloy) and CoFe alloy. Particularly, uniaxial anisotropy constant K _u is large, it is possible to use a magnetic material exhibiting a perpendicular magnetic anisotropy. When a material having a large anisotropy constant _Ku is used, the domain wall width when a magnetic field or current is not applied is narrow. Therefore, in the present embodiment, the use of anisotropy constant K _u is greater material as the magnetic wire 100, easily effect is obtained domain wall width is expanded when given a magnetic field, preferable. Examples of such materials include one or more elements selected from the group Fe, Co, Ni, Mn, Cr and one or more elements selected from the group Pt, Pd, Ir, Ru, Rh. There are alloys containing The value of the uniaxial anisotropy constant can also be adjusted by the composition of the magnetic material constituting the magnetic layer, crystal regularity by heat treatment, and the like.

  Alternatively, a magnetic material having a crystal structure of an hcp (hexagonal close-packed structure) structure (hexagonal close-packed structure) and exhibiting perpendicular magnetic anisotropy can be used. As such a magnetic material, a material containing a metal containing Co as a main component is typical, but other metals having an hcp structure can also be used.

  The magnetization direction of the magnetic fine wire 100 may be perpendicular or parallel to the fine wire direction, but it is preferable to make the magnetization direction perpendicular, for example, because a current value required to move the domain wall can be reduced.

  When the thin wire direction of the magnetic wire 100 is formed in a direction perpendicular to the substrate, the magnetization direction is perpendicular to the thin wire direction of the magnetic wire 100 because the easy axis of magnetic anisotropy is in the film plane. Can be directed. Examples of materials having a large magnetic anisotropy and an easy axis of magnetic anisotropy in the film plane include Co, CoPt alloy, and CoCrPt alloy. CoPt or CoCrPt may be an alloy. These are metal crystals in which the c axis of hcp is in the film plane. Further, in any of the above material groups, an additive element may be added.

  When the fine wire direction of the magnetic fine wire 100 is formed in a direction parallel to the substrate surface, the easy axis of magnetic anisotropy is in the direction perpendicular to the film surface, so that the magnetization direction is the fine wire direction of the magnetic fine wire 100. Can be oriented vertically. Examples of materials that realize these include a Co layer, a CoPt layer, an FePt layer, a (Co / Ni) laminated film, a TbFe layer, and the like in which the c axis of hcp is oriented in the direction perpendicular to the film surface. CoPt may be an alloy. In the case of a TbFe layer, when Tb is 20 atomic% or more and 40 atomic% or less, the TbFe layer exhibits perpendicular anisotropy. Further, in any of the above material groups, an additive element may be added.

  In addition, as the material of the magnetic wire 100, a material exhibiting perpendicular magnetic anisotropy, which is an alloy of a rare earth element and an iron group transition element, can be used. Specific examples include GdFe, GdCo, GdFeCo, TbFe, TbCo, TbFeCo, GdTbFe, GdTbCo, DyFe, DyCo, DyFeCo, and the like.

  In addition, since the magnetic fine wire 100 does not generate a magnetization distribution in a cross section perpendicular to the thin wire direction, it is desirable that one side or diameter of the cross section be in the range of 2 nm to 100 nm. As the length of the magnetic fine wire 100 in the fine wire direction is increased, a larger number of magnetic domains can be included. However, if the total length becomes extremely long, the electrical resistance of the entire magnetic thin wire 100 becomes high, and therefore it is typically preferable that the range is from 100 nm to 10 μm.

  The magnetic fine wire 100 can be provided with a region having a cross-sectional area such as a depression different from other portions at regular intervals in the fine wire direction. In this case, for the domain wall, the pinning potential is higher than in the case where there is no depression, and it becomes easier to stand still. However, on the other hand, the current required to make a transition from the stationary state to the moving state increases. Even in such a case, the magnetic memory element of the present embodiment can increase the width of the domain wall by the action of the assist unit. Therefore, the domain wall can be moved with a smaller current. high.

  These magnetic materials used for the magnetic wire 100 include Ag, Cu, Au, Al, Mg, Si, Bi, Ta, B, C, O, N, Pd, Pt, Zr, Ir, W, and Mo. , Nb, H and other nonmagnetic elements can be added to adjust the magnetic properties, or various physical properties such as crystallinity, mechanical properties, and chemical properties can be adjusted.

(simulation result)
A simulation for comparing the magnetic memory element 1 of this embodiment and the magnetic memory element according to the comparative example was performed. The simulation results are shown in FIGS. 7 (a) to 7 (c). The magnetic memory element of the comparative example has a configuration in which the wiring 210 for applying a magnetic field to the magnetic thin wire 100 is not provided. The magnetic memory elements of this embodiment and the comparative example are simulated under the same conditions except for the presence / absence of magnetic field application to magnetic materials of the same material and size. In this simulation, an initial condition is a magnetization arrangement in which a region having a magnetization direction opposite to that of the surrounding is provided in a fine-line-shaped magnetic material simulating the magnetic fine wire 100, and the current is measured using a micromagnetic simulation. Or a time change of the magnetic structure when a magnetic field is applied.

FIG. 7A and FIG. 7B show the domain wall width time when a magnetic field is applied from time t ₂ to time t ₃ and current is passed after time t _{1 in} accordance with the procedure described in this embodiment. It is a simulation result which shows progress and the time passage of magnetization distribution. FIGS. 7 (a) broken lines and FIG. 7 (c), in the magnetic memory element of the comparative example, the magnetic field is not applied, the time of the time course and magnetization distribution of the domain wall width in the case where a current flows only after time t ₁ It is a simulation result which shows progress. As can be seen from FIGS. 7A, 7B, and 7C, in each of the magnetic memory elements of this embodiment and the comparative example, the time at which the domain wall width starts to increase and the time at which the domain wall moves Can be seen to be synchronized. Moreover, in this embodiment, it turns out that the domain wall width has expanded during the application of a magnetic field. Therefore, in the present embodiment as compared with the comparative example, the time from the time t ₁ which begins to conduct current until time domain wall begins to move is significantly reduced, it is possible to move the fast domain wall as compared with the comparative example. The time until the domain wall starts to move can be shortened by increasing the magnitude of the current, which means that there is an effect of reducing the current when the domain wall is moved by flowing the current for a certain period of time. Can do.

  Next, a method for manufacturing a magnetic memory element according to a first modification of the first embodiment will be described with reference to FIGS.

  First, as shown in FIG. 8A, a wafer (not shown) having an insulating film 10 formed on the upper surface is prepared, and a current is applied to the insulating film 10 using a lithography technique and RIE (Reactive Ion Etching). A groove for the wiring 210 that generates a magnetic field is formed. Subsequently, a conductive film such as Cu is formed in the groove to form a wiring 210. After that, an insulating film 12 such as silicon oxide is stacked, and the grooves for the reading portion 120 and the lower electrode 122a and the lower electrode 112a of the writing portion are formed by using a lithography technique and RIE. For example, a conductive film such as Cu is formed, and the lower electrode 122a and the lower electrode 112a are formed. Thereafter, an insulating film (not shown) is further formed, and the insulating film is flattened using, for example, CMP (Chemical Mechanical Polishing) or the like to expose the upper surfaces of the lower electrode 122a and the lower electrode 112a.

  Next, the magnetic layer 14, the nonmagnetic layer 16, the magnetic layer 18, and the protective film 20 are formed in this order (FIG. 8A). The magnetic layer 14 becomes the magnetic wire 100. The material of the nonmagnetic layer 16 is, for example, MgO, and the nonmagnetic layer 16 becomes the nonmagnetic layer 114 and the nonmagnetic layer 124 of the writing unit 110 and the reading unit 120. The magnetic layer 18 becomes the magnetization fixed layer 116 and the magnetization fixed layer 126 of the writing unit 110 and the reading unit 120. Further, for example, Ta is used as the protective film 20, and the upper electrodes 112b and 122b of the writing unit 110 and the reading unit 120 are used. A wafer in which the magnetic layer 14, the nonmagnetic layer 16, the magnetic layer 18, and the protective film 20 are stacked is put in a vacuum furnace in a magnetic field, and annealed in a magnetic field under conditions of 270 ° C. for 10 hours, for example. Unidirectional anisotropy is imparted to the magnetic layers 14 and 18. Thereafter, the protective film 20, the magnetic layer 18, the nonmagnetic layer 16, and the magnetic layer 14 are patterned into a planar shape of the magnetic wire 100 by using a lithography technique and RIE (FIG. 8A).

  Next, using the lithography technique and RIE, the protective film 20, the magnetic layer 18, and the nonmagnetic layer 16 are patterned into the planar shape of the magnetic wire 100 to form the writing unit 110 and the reading unit 120 (FIG. 8). (B)). Subsequently, after the interlayer insulating film 22 is deposited, the interlayer insulating film 22 is flattened to expose the upper electrodes 112b and 122b of the writing unit 110 and the reading unit 120 (FIG. 8B).

  Next, using the lithography technique and RIE, a contact hole connected to the magnetic wire 100 is formed in the interlayer insulating film 22, and this contact hole is filled with a conductive film material, thereby forming electrodes 104a and 104b (FIG. 8 (c)). Thereby, the magnetic memory element is completed.

  As described above, according to the first embodiment, it is possible to reduce the current density required for transition from the stationary state to the moving state, and it is possible to stably move the domain wall. .

(Second Embodiment)
FIG. 9 shows a magnetic memory element according to the second embodiment. The magnetic memory element 1 according to the second embodiment includes a magnetic wire 100 having a plurality of magnetic domains 101 _{1 to} 101 _n (n is an integer), electrodes 104 a and 104 b for passing a current from the current source 150 to the magnetic wire 100, A spin wave generator 170 that generates spin waves in the magnetic wire 100. Although not shown, the magnetic memory element 1 of the second embodiment is also provided with a writing unit and a reading unit as in the first embodiment.

The spin wave generator 170 includes a magnetic layer 172 connected to one end of the magnetic wire 100 and extending in a direction perpendicular to the direction of the magnetic wire 100, a nonmagnetic layer 174 provided on the magnetic layer 172, and a nonmagnetic material. The magnetization fixed layer 176 provided on the layer 174, and the electrodes 177 a and 177 b that allow the current from the current source 180 to flow between the magnetic layer 172 and the magnetization fixed layer 176 are provided.
In FIG. 9, the nonmagnetic layer 174 and the magnetization fixed layer 176 of the spin wave generator 170 are provided on the surface of the magnetic layer 172 on the same side as the magnetic wire 100, but the first modification shown in FIG. As described above, it may be provided on the surface of the magnetic layer 172 opposite to the magnetic wire 100. In this case, the electrode 177a is also used as the electrode 104b.

  Further, the magnetization fixed layer 176 is increased in thickness to increase thermal disturbance resistance, or the antiferromagnetic layer 178 for fixing magnetization is opposite to the nonmagnetic layer 174 as shown in FIG. You may provide in the surface of the magnetization fixed layer 176 of the side. Although not shown in FIG. 9, the antiferromagnetic layer 178 may also be provided on the surface of the magnetization fixed layer 176 opposite to the nonmagnetic layer 174 in FIG. The current source 150 and the current source 180 may share some electrodes, but are configured to be able to control on and off of the current independently of each other.

  The magnetization directions of the magnetic layer 172 and the magnetization fixed layer 176 may be parallel (or antiparallel) to each other or perpendicular to each other.

In the present embodiment, the domain wall of the magnetic wire 100 is moved in the following procedure. First, as shown in FIG. 4 (c), between the time _{t 2} to time _{t 3,} a current flows 185 by a current source 180. This procedure is called an assist procedure. When the assist procedure is executed, a spin-polarized current flows in at least a part of the magnetic wire 100 or the magnetic layer 172, and thus spin torque is applied, so that the magnetization direction changes in the magnetic wire 100 or the magnetic layer 172. At this time, if the magnetization direction in the region receiving the spin torque in the magnetic layer 172 is reversed, unintended writing is performed. This can be prevented and the change in the magnetization direction can be kept to 90 degrees or less, or the magnetization precession state Need to be generated. In this case, since the magnetization change propagates as a spin wave from the magnetic layer 172 to the magnetic wire 100, the domain wall width in the magnetic wire 100 is expanded as compared with that before the current flows.

At time t ₁ , a current is passed through the magnetic wire 100 by the current source 150. If this current value is equal to or greater than the threshold value, the position of the domain wall in the magnetic wire 100 moves in the direction in which the electron current flows, that is, the direction opposite to the current. When the current is turned off, the domain wall movement stops, so that the domain wall movement distance can be controlled by the current flow time. That is, in the present embodiment, the spin wave generator 170 assists the movement of the domain wall and is also called an assist unit.

In order to prevent unintended magnetization reversal in the spin wave generator 170, for example, the angle formed by the magnetization direction of the magnetization fixed layer 176 and the magnetization direction in the vicinity of the interface between the magnetic layer 172 and the nonmagnetic layer 174 is If the angle is in the range of 45 degrees to 135 degrees, unintended magnetization reversal does not occur even if the current 185 continues to flow. Therefore, an angle formed by the magnetization direction of the magnetization fixed layer 176 and the magnetization direction in the region near the interface between the magnetic layer 172 and the nonmagnetic layer 174 may be, for example, perpendicular. If the magnetization direction of the magnetization fixed layer 176 and the magnetization direction of the magnetic layer 172 are perpendicular to each other, there is also an advantage that the current required for causing the magnetization change can be reduced. Further, when the angle formed by the magnetization direction of the magnetization fixed layer 176 and the magnetization direction in the region near the interface between the magnetic layer 172 and the nonmagnetic layer 174 is 0 degree, that is, parallel, the current 185 is supplied from the magnetization fixed layer 176. By flowing with the polarity flowing through the magnetic layer 172, magnetization fluctuation can be given to the magnetic layer 172.
When the angle formed by the magnetization direction of the magnetization fixed layer 176 and the magnetization direction in the region near the interface between the magnetic layer 172 and the nonmagnetic layer 174 is 180 degrees, that is, antiparallel, the current 185 is supplied from the magnetic layer 172. By flowing with the polarity flowing in the magnetization fixed layer 176, magnetization fluctuation can be applied to the magnetic layer 172. However, when the magnetization direction of the magnetization fixed layer and the magnetization direction of the magnetic layer 172 are parallel or antiparallel, the magnitude of the current 185 is equal to or greater than a certain threshold value, and the threshold value is determined by the value of the current 185. If it is above, since the magnetization direction will be reversed in the region of the magnetic wire 100 that receives the spin torque, the magnitude of the current 185 or the flow time must be less than the respective threshold values. For example, if the magnitude of the current 185 is less than the threshold value, the restoring force due to the exchange interaction inside the magnetic layer 172 works together with the action due to the spin torque, so that stable magnetization oscillation occurs, and the current 185 is controlled over time. Even if it is not performed, it is desirable because a spin wave is continuously generated. In particular, by reducing the plane size of the nonmagnetic layer 174, the ratio of exchange interaction to the spin torque can be increased, so that it is difficult to cause magnetization reversal. In addition, by making the waveform of the current 185 a periodic pulse current or an alternating current, for example, the spin torque can be weakened before the magnetization reversal occurs to prevent the reversal. That is, in the second embodiment, the magnetization fluctuation can be stably introduced into the magnetic fine wire 100, and therefore, a state in which the domain wall width in the magnetic fine wire 100 is enlarged is obtained over a long distance in the fine wire direction. Therefore, even if the magnitude of the current passed by the current source 150 is suppressed, it is possible to stably move a large number of domain walls.

  In the magnetic memory element 1 of the second embodiment and the first modification example, the fine wire direction of the magnetic fine wire 100 is arranged perpendicular to the substrate surface (for example, the upper surface of the substrate). Like the magnetic memory element 1 of the 2nd modification shown, you may arrange | position in parallel with respect to a substrate surface. In this case, the layers 172, 174, and 176 of the spin wave generator 170 are provided in parallel to the thin wire direction of the magnetic wire 100. In FIG. 11, the current source 180 shown in FIG. 9 or 10 is also used as the current source 150 that supplies current to the magnetic wire 100. In this case, the electrode 177b is also used as the electrode 104b.

  Next, the material of each layer of the magnetic memory element according to the second embodiment and its modification will be described.

  The material that can be used as the material of the magnetic wire 100 is the same as that of the first embodiment.

  The materials of the magnetic layer 172 and the magnetization fixed layer 176 of the spin wave generator 170 can be selected from various magnetic materials as in the first embodiment. The magnetic layer 172, the magnetization fixed layer 176, and the magnetic wire 100 may be the same material or different.

As the material of the antiferromagnetic layer used for fixing the magnetization of the magnetization fixed layer 176, Fe—Mn, Pt—Mn, Pt—Cr—Mn, Ni—Mn, Pd—Mn, Pd—Pt—Mn, Ir It is desirable to use —Mn, Pt—Ir—Mn, NiO, Fe ₂ O ₃ , a magnetic semiconductor, or the like.

  As the material of the nonmagnetic layer 174, a nonmagnetic metal or an insulating thin film can be used. As the nonmagnetic metal, any element of Au, Cu, Cr, Zn, Ga, Nb, Mo, Ru, Pd, Ag, Hf, Ta, W, Pt, Bi, or any of these elements An alloy containing one or more kinds can be used. Further, the thickness of the nonmagnetic layer 174 needs to be sufficiently small so that the magnetostatic coupling between the magnetization fixed layer 176 and the magnetic layer 172 is smaller than the spin diffusion length of the nonmagnetic layer 174. Specifically, It is desirable to be within the range of 0.2 nm or more and 20 nm or less.

Insulating materials that can be used for the nonmagnetic layer 174 include Al ₂ O ₃ , SiO ₂ , MgO, AlN, Bi ₂ O ₃ , MgF ₂ , CaF ₂ , SrTiO ₃ , AlLaO ₃ , Al—N—O, Si —N—O, nonmagnetic semiconductor (ZnO, InMn, GaN, GaAs, TiO ₂ , Zn, Te, or those doped with a transition metal) can be used.
These compounds do not need to have a completely accurate composition in terms of stoichiometry, and may be deficient or excessive or deficient in oxygen, nitrogen, fluorine, or the like. The thickness of the nonmagnetic layer 174 made of this insulating material is preferably in the range of 0.2 nm to 5 nm.

  As described above, according to the second embodiment, it is possible to reduce the current density necessary for making the transition from the stationary state to the moving state, and it is possible to stably move the domain wall. .

(Third embodiment)
FIG. 12 shows a magnetic memory element according to the third embodiment. The magnetic memory element 1 according to the third embodiment includes a magnetic wire 100 having a plurality of magnetic domains 101 _{1 to} 101 _n (n is an integer), electrodes 104a and 104b for passing a current from the current source 150 to the magnetic wire 100, A magnetic layer 130 provided so as to surround the magnetic wire 100 along the thin wire method of the magnetic wire 100 and a wiring 230 provided so as to be close to the magnetic wire 100 in the magnetic layer 130 are provided. Although not shown, the magnetic memory element 1 of the third embodiment is also provided with a writing unit and a reading unit as in the first embodiment.

  In FIG. 12, the wiring 230 is provided so as to extend in a direction orthogonal to the direction of the fine wire 100, but as in the first modification of the third embodiment shown in FIG. In addition, the magnetic fine wire 100 may be provided so as to extend along the fine wire direction. The magnetic layer 130 and the wiring 230 constitute a spin wave generator.

  The magnetic layer 130 is made of an insulating magnetic material or a highly conductive magnetic material. When the magnetic layer 130 is made of an insulating magnetic material, the magnetic layer 130 may be directly connected to the magnetic wire 100. In this case, since the distance between the magnetic wire 100 and the magnetic layer 130 is short, the spin wave generated in the magnetic layer 130 can be directly propagated into the magnetic wire 100, and fluctuation transmission efficiency is increased. When the magnetic layer 130 is made of a highly conductive magnetic material, it is necessary to sandwich a nonmagnetic insulator (not shown) between the magnetic layer 130 and the magnetic wire 100, and it is necessary to electrically insulate. Thus, the magnetic layer 130 is a layer that generates a spin wave and also a layer that propagates the spin wave to the magnetic wire 100.

  When the magnetic layer 130 is made of an insulating material, the wiring 230 may be embedded in the magnetic layer 130. Or the wiring 230 is arrange | positioned in the position close | similar to the magnetic layer 130 through the insulator 232 as shown in FIG. The wiring 230 extends in a direction parallel to the substrate surface as shown in FIGS. 12 and 14A, or a direction perpendicular to the substrate surface as shown in FIGS. 13 and 14B. It does not matter if it extends to 14A and 14B are top views when the magnetic memory element shown in FIGS. 12 and 13 is viewed from above the substrate, respectively.

In 3rd Embodiment, the movement of the magnetic wall of the magnetic wire 100 is performed in the following procedures. First, during the period from time _{t 2} to _{t 3,} a current flows to the wiring 230. This procedure is called an assist procedure.
When the assist procedure is executed, fluctuation occurs in the direction of the magnetization 131 in at least a partial region of the magnetic layer 130, and the fluctuation of the magnetization 131 propagates in the magnetic layer 130 as a spin wave. Further, since a magnetostatic interaction acts between the magnetization 131 in the magnetic layer 130 and the magnetization in the magnetic wire 100, fluctuation is given to the magnetization in the magnetic wire 100, and a spin wave is generated in the magnetic wire 100. Is propagated. Therefore, as in the case of the second embodiment, the domain wall width in the magnetic wire 100 is wider than before the current flows. Note that the timing of supplying a current using the current source 150 is the same as in the first embodiment. That is, in the present embodiment, the magnetic layer 130 and the wiring 230 assist the movement of the domain wall and constitute an assist unit.

  As a result, according to the third embodiment, it is possible to reduce the current density required for transition from the stationary state to the moving state, and it is possible to stably move the domain wall.

  When the magnetic memory element according to the third embodiment is used, fluctuations can be simultaneously applied to a plurality of domain walls in the magnetic wire, and therefore the domain walls in the magnetic wire can be moved simultaneously. Furthermore, when the magnetic layer 130 is made of an insulating magnetic material, the distance between the magnetic layer 130 and the magnetic wire 100 can be reduced, so that fluctuation can be efficiently given.

  Unlike the magnetic memory element 1 according to the second modification of the third embodiment shown in FIG. 15, the magnetic layer 130 does not have to be provided so as to surround the magnetic wire 100, and is disposed in the vicinity of the entire magnetic wire 100. It should be. In the second modification shown in FIG. 15, the magnetic layer 130 is provided between the magnetic wire 100 and the wire 230, and the wire 230 extends in a direction orthogonal to the magnetic wire 100 without intersecting the wire direction. Exist.

  Further, unlike the magnetic memory element 1 according to the third modification of the third embodiment shown in FIG. 16, the magnetic layer 130 does not have to be provided so as to surround the magnetic wire 10, and is close to the entire magnetic wire 100. It only has to be arranged. In the third modification shown in FIG. 16, the magnetic layer 130 is provided between the magnetic wire 100 and the wire 230, and the wire 230 extends in a direction along the direction of the magnetic wire 100. Yes.

  Further, unlike the magnetic memory element 1 according to the fourth modification of the third embodiment shown in FIG. 17, the magnetic layer 130 does not have to be disposed close to the entire magnetic wire 100, and one of the magnetic wires 100. May be close to the region of the part. In this case, it is desirable that at least one domain wall of the magnetic wire 100 is close to the magnetic layer 130 because an effect of expanding the domain wall width is easily obtained.

  Further, like the magnetic memory element 1 according to the fifth modification of the third embodiment shown in FIG. 18, the magnetic layer 130 may be disposed so as to surround a partial region of the magnetic wire 100. In this case, it is desirable that at least one or more domain walls of the magnetic wire 100 be disposed so as to surround the magnetic layer 130 because an effect of expanding the domain wall width is easily obtained.

  Further, a coil 235 may be provided so as to surround the magnetic memory element 1 and the magnetic layer 130 instead of the wiring 230 as in the magnetic memory element 1 according to the sixth modification of the third embodiment shown in FIG. A spin wave is generated in the magnetic layer 130 by a magnetic field generated by passing a current through the coil 235, and the generated spin wave is propagated to the magnetic wire 100. In the sixth modification, a plurality of magnetic memory elements 1 may be provided between the coils 235. In this case, the magnetic field generation source (coil 235) can be shared among the plurality of magnetic memory elements, which is advantageous from the viewpoint of high integration of the magnetic memory elements.

  In the case where an insulating magnetic material is used as the magnetic layer 130 used in the magnetic memory element 1 of the third embodiment and its modification, a ferrite-based oxide such as yttrium iron garnet (YIG) or manganese ferrite is used. It is preferable. This is because the transmission loss of the spin wave can be reduced because the attenuation coefficient is small.

  However, it is not limited to these materials, and other magnetic oxides including iron, cobalt, and nickel can also be used. Examples include spinel oxide and antiferromagnetic oxide.

(Fourth embodiment)
A magnetic memory element according to the fourth embodiment is shown in FIG. The magnetic memory element 1 according to the fourth embodiment includes a magnetic wire 100 having a plurality of magnetic domains 101 _{1 to} 101 _n (n is an integer), electrodes 104 a and 104 b that flow current from the current source 150 to the magnetic wire 100, And a spin wave generator 240. The spin wave generator 240 is provided on the magnetic layer 242 provided close to the whole or part of the magnetic wire 100, the nonmagnetic layer 244 provided on the magnetic layer 242, and the nonmagnetic layer 244. A magnetization fixed layer 246 and electrodes 247 a and 247 b that allow current from the current source 248 to flow between the magnetic layer 242 and the magnetization fixed layer 246 are provided. Although not shown, the magnetic memory element 1 of the fourth embodiment is also provided with a writing unit and a reading unit as in the first embodiment. Further, the magnetization direction of the magnetization fixed layer 246 is fixed. The magnetization direction is fixed by increasing the film thickness or by providing an antiferromagnetic layer on the surface opposite to the nonmagnetic layer 244.

In the present embodiment, the domain wall of the magnetic wire 100 is moved in the following procedure. First, during the period from time _{t 2} to time _{t 3,} a current flows to the current source 248. This procedure is called an assist procedure. When the assist procedure is executed, a spin-polarized current flows into the magnetic layer 242, and the magnetization 243 of at least a part of the region receives the spin torque and fluctuates. This fluctuation of the magnetization 243 propagates in the magnetic layer 242 as a spin wave. Further, since a magnetostatic interaction works between the magnetization 243 in the magnetic layer 242 and the magnetization in the magnetic wire 100, fluctuation is given to the magnetization in the magnetic wire 100, and a spin wave is generated in the magnetic wire 100. Propagate. Therefore, the domain wall width in the magnetic wire 100 is wider than before the current is passed. That is, in the present embodiment, the spin wave generation unit 240 assists the movement of the domain wall and is also referred to as an assist unit. Note that the timing of supplying a current using the current source 150 is the same as in the first embodiment.

  When the magnetic layer 242 is made of an insulator, a spin wave generator 240A including a voltage source 249 may be used instead of the current source 248 as in a modification of the fourth embodiment shown in FIG. Good. When the magnetic layer 242 is made of an insulator, the magnetic layer 100 may be in contact with the magnetic layer 242. Alternatively, all or part of the magnetic layer 100 may be embedded in the magnetic layer 242. Thus, when the magnetic layer 100 is in direct contact with the magnetic layer 242, the magnetization fluctuation generated in the magnetic layer 242 can be efficiently transmitted into the magnetic layer 100, and the domain wall width in the magnetic layer 100 is increased. There is a merit that it can be expanded. When the magnetic layer 242 is made of a highly conductive material, an insulator (not shown) needs to be sandwiched between the magnetic layer 100 and the magnetic layer 242 to be electrically insulated.

  When a large number of magnetic storage elements of this embodiment are used side by side, the magnetic layer 242, the nonmagnetic layer 244, and the magnetization fixed layer 246 may be shared between a plurality of adjacent magnetic storage elements. By doing so, the magnetic memory element can be highly integrated. Also in this case, if no current is passed through the magnetic wire 100, only a spin wave is generated in the magnetic layer 242, and the domain wall in the magnetic wire 100 does not move. Therefore, each magnetic element can be controlled independently. it can.

  As described above, according to the fourth embodiment, similarly to the second embodiment, it is possible to reduce the current density necessary for transitioning the domain wall from the stationary state to the moving state, and to reduce the domain wall. The movement can be performed stably.

(Fifth embodiment)
The magnetic memory element according to the fifth embodiment is shown in FIGS. 22 (a) and 22 (b). A sectional view of the magnetic memory element 1 of the fifth embodiment is shown in FIG. 22A, and a top view thereof is shown in FIG.

A magnetic memory element 1 according to the fifth embodiment includes a magnetic wire 100 having a plurality of magnetic domains 101 _{1 to} 101 ₈ , electrodes 104 a and 104 b for passing a current from a current source 150 to the magnetic wire 100, and a piezoelectric unit 250. ing. The piezoelectric portion 250 is provided on the piezoelectric layer 252 so as to surround at least a part of the magnetic wire 100 (all regions in the drawing), and a voltage from the voltage source 256 is provided. Are applied to the piezoelectric layer 252, and electrodes 254a and 254b are provided. Although not shown, the magnetic memory element 1 of the fifth embodiment is also provided with a writing unit and a reading unit as in the first embodiment.

In the fifth embodiment, the domain wall is moved in the following procedure. First, during the period from time _{t 2} to _{t 3,} applying a voltage to the electrode 254. This procedure is called an assist procedure. When the assist procedure is executed, crystal distortion occurs in the piezoelectric layer 252 as vibration, and propagates in the piezoelectric layer 252 as an elastic wave from the region in contact with the electrode 254 of the piezoelectric layer 252 to the surrounding region. As a result, the magnetic fine wire 100 receives stress through the interface with the piezoelectric layer 242, and the magnetic anisotropy of the magnetic fine wire 100 changes due to the inverse magnetostriction effect. As a result, fluctuation is given to the magnetization in the magnetic wire 100. Therefore, the domain wall width in the magnetic wire 100 is wider than before the current is passed. As a result, it is possible to significantly reduce the current value required to shift the domain wall. That is, in this embodiment, the piezoelectric part 250 assists the movement of the domain wall and is also called an assist part. In the fifth embodiment, stress is applied to the entire interface between the piezoelectric layer 242 and the magnetic wire 100, and therefore, the entire region in the vicinity of the interface in the magnetic wire 100 is strained, and the domain wall width in the region is expanded. . Therefore, in the embodiment using the current magnetic field by the wiring, the action is reduced in inverse proportion to the distance, whereas in the fifth embodiment, the entire domain wall to which the action is applied can be given a uniform action to increase the width. There is a merit that you can. Even when the piezoelectric layer 242 is in contact with a part of the magnetic wire 100, the magnetization fluctuation caused by the strain propagates through the magnetic wire 100 as a spin wave, which is effective. However, the piezoelectric layer 242 is in contact with the magnetic wire 100. A large interface area is preferable because the uniformity of the action is improved. In particular, it is preferable that the piezoelectric layer 252 extends over the entire thin wire direction of the magnetic thin wire 100 because the above effect can be obtained over the entire wire. As the most preferred example, when the piezoelectric layer 252 surrounds the magnetic wire 100, it is possible to stably increase the width of all the domain walls in the magnetic wire 100 at once.

  Furthermore, another advantage of the fifth embodiment is an effect of reducing power consumption. Since the application of stress to the magnetic wire 100 using the piezoelectric layer 252 is voltage-driven, the power consumption required to apply the distortion is significantly smaller than, for example, an embodiment using a current magnetic field by wiring, Therefore, when combined with the fact that the current required for the domain wall movement can be reduced by the assist effect due to the domain wall width expansion, the power consumption required for the domain wall movement is significantly reduced. It is estimated that the current value required to move the domain wall can be reduced by one digit or more according to this embodiment.

  The propagation characteristic of the elastic wave propagating in the piezoelectric layer 252 depends on the crystallinity of the piezoelectric body and propagates in a direction corresponding to the crystal orientation. In particular, in a single crystal or a uniaxially oriented piezoelectric material, uniform surface acoustic waves are excited, so it is desirable to form the piezoelectric layer 135 from a single crystal or a uniaxially oriented piezoelectric material.

Examples of the material of the piezoelectric body 252 include potassium sodium tartrate (KNaC ₄ H ₄ O ₆ ), zinc oxide (ZnO), aluminum nitride (AlN), and lead zirconate titanate (PZT (Pb (Zr, Ti) O ₃ ). )), Lead lanthanum zirconate titanate (PLZT), crystal (SiO ₂ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), niobic acid Potassium (KNbO ₃ ), langasite crystals (eg, La ₃ Ga ₅ SiO ₁₄ ), potassium sodium tartrate tetrahydrate (KNaC ₄ H ₄ O ₆ .4H ₂ O), and the like can be used. Further, based on these piezoelectric materials, an additive element may be added to adjust the characteristics. The piezoelectric body 252 may have a layer structure in which a plurality of layers made of these materials are stacked.

  The material of the magnetic wire 100 that can be used in the fifth embodiment is the same as that in the first embodiment. In particular, a material with a large absolute value of the magnetostriction constant has a large change in magnetic anisotropy when subjected to a certain stress, and therefore the magnetization direction changes greatly even when a slight strain is applied. This is desirable because the effect of expanding the width is increased and the current value required for domain wall motion can be reduced. Examples of the material having a large magnetostriction constant include alloys such as Fe, Co, Ni and Mn, alloys of Fe, Co, Ni and platinum, and rare earth alloys such as Fe, Co, Ni and Tb, Sm and Eu. In addition, as the material of the magnetic wire 100 of the fifth embodiment, a material whose magnetostriction constant is increased by adding an additive element to the same material as that of the first embodiment can be used. As an example, the magnetostriction constant of a magnetic material to which Ni element is added shifts in the negative direction as compared with a material to which Ni element is not added. Therefore, by increasing the content of Ni element, a magnetic material having a magnetostriction constant having a negative sign and a large absolute value can be obtained. As another example, a magnetic material to which a small amount of oxygen is added has a magnetostriction constant shifted in the positive direction as compared with a material to which oxygen is not added. Therefore, by adding oxygen to the magnetic material, a magnetic material having a magnetostriction constant having a positive sign and a large absolute value can be obtained.

  A magnetic memory element according to a modification of the fifth embodiment is shown in FIG. In the magnetic memory element of this modification, electrodes 254 a and 254 b for applying a voltage to the piezoelectric layer 252 are provided in parallel to the thin wire direction of the magnetic wire 100. FIG. 23 is a cross-sectional view, and the piezoelectric layer 252 is provided so as to surround the magnetic wire 100, but the electrodes 254 a and 254 b are provided in part of the piezoelectric layer 252.

(Sixth embodiment)
A magnetic storage device according to the sixth embodiment is shown in FIG. As shown in FIG. 24, the magnetic memory device 280 of the sixth embodiment includes a plurality of magnetic wires 100, a piezoelectric layer 252 provided so as to surround each magnetic wire, and electrodes for applying a voltage to the piezoelectric layer 252. 254a and 254b. In FIG. 24, the piezoelectric layer 252 surrounds the periphery of each magnetic wire 100. However, in order to ensure more reliable insulation, for example, amorphous SiO ₂ , amorphous Al is interposed between the magnetic wire 100 and the piezoelectric layer 252. An insulating material such as ₂ O ₃ may be provided.

  Although not shown, each magnetic wire 100 is provided with an electrode for passing a current through the magnetic wire in the magnetic memory element of the fifth embodiment, so that a current can flow through the magnetic wire 100. Is done. Although not shown, a magnetic layer is connected to at least one magnetic wire 100, and a writing unit and a reading unit similar to those in the fifth embodiment are connected to the magnetic layer. In this magnetic memory device 280, as shown in FIG. 24, the magnetic memory element assist procedure of the fifth embodiment is executed by performing piezoelectric driving on a plurality of magnetic wires 100 collectively. Therefore, the domain wall motion in the magnetic wire 100 can be performed in the same procedure as the magnetic memory element of the fifth embodiment. The writing method and reading method are the same as those of the magnetic memory element of the fifth embodiment. That is, the magnetic storage device of the sixth embodiment includes a plurality of magnetic storage elements of the fifth embodiment, and the plurality of magnetic storage elements share an assist unit.

In the magnetic storage device 280 of the sixth embodiment, as shown in FIG. 24, electrodes 254 a and 254 b for applying a voltage to the piezoelectric layer 252 are provided along a direction parallel to the thin wire direction of each magnetic wire 100. However, a configuration in which the plurality of magnetic thin wires 100 are provided along the direction perpendicular to the thin wire direction is also conceivable. This case is shown in FIG. 25 as a modification of the sixth embodiment. As shown in FIG. 25, the magnetic storage device 280A of this modified example includes a plurality of magnetic wires 100 arranged in a matrix (row direction and column direction) so that the directions of the thin wires are parallel to each other, and their magnetic properties. And an insulator 258 provided so as to surround the fine wire 100. In addition, a plurality of word lines WL and a plurality of bit lines BL intersecting these word lines WL are provided on one surface of the upper surface or the lower surface of the assembly including a plurality of magnetic thin wires 100 and insulators 258. Yes.
In FIG. 25, a plurality of word lines WL and a plurality of bit lines BL are provided on the upper surface of an assembly made up of magnetic thin wires 100 and insulators 258. The plurality of word lines WL are provided corresponding to, for example, columns of the plurality of magnetic thin lines 100 arranged in a matrix, and the plurality of bit lines BL correspond to, for example, rows of the plurality of magnetic thin lines 100 arranged in a matrix. Is provided. The surface on which the plurality of word lines WL and the plurality of bit lines BL are provided is parallel to the surface orthogonal to the thin line direction of the plurality of magnetic thin wires 100. In the intersection region between each word line WL and each bit line BL, the word line WL and the bit line BL are in contact with each other, and the upper surface of the corresponding magnetic thin wire 100 is in contact therewith. Further, a piezoelectric layer 252 is provided on the plurality of word lines WL and the plurality of bit lines BL, and an electrode 254 is provided on the piezoelectric layer 252. The electrode 254 is connected to a voltage source 256 that applies a voltage to the piezoelectric layer 252.

  In the modified example configured as described above, when a voltage is applied to the electrode 254, crystal distortion occurs in the piezoelectric layer 252 as vibration, and propagates in the piezoelectric layer 252 as an elastic wave. As a result, the upper surface of each magnetic wire 100 receives stress through the word line WL and the bit line BL, and the magnetic anisotropy of the magnetic wire 100 changes due to the inverse magnetostriction effect. As a result, fluctuation is given to the magnetization in the magnetic wire 100. Therefore, the domain wall width in the magnetic wire 100 is wider than before the current is passed. As a result, it is possible to significantly reduce the current value required to shift the domain wall.

  In FIG. 25, the word line WL and the bit line BL are provided on the upper surface of the aggregate made up of the magnetic thin wire 100 and the insulator 258, but may be provided on the lower surface. In this case, the piezoelectric layer 252 and the electrode 254 may be provided on the upper surface side or may be provided on the lower surface side.

  Further, the memory chip 285 can be realized by providing a plurality of magnetic storage devices 280 and 280A shown in FIG. 24 or FIG. 25 as one block along the column direction or the row direction. An example is shown in FIG. Piezoelectric driving is performed in units of blocks, but a large capacity memory chip can be realized by providing a plurality of these blocks on the chip. Transistors (not shown) are arranged below the plurality of blocks.

(Seventh embodiment)
A magnetic memory device according to the seventh embodiment will be described with reference to FIGS. FIG. 27 shows a circuit diagram of a magnetic memory device according to the seventh embodiment, and FIG. 28 shows a perspective view thereof.

The magnetic storage device of the seventh embodiment has a memory cell array 300. The memory cell array 300 includes a plurality of memory cells arranged in a matrix, and each memory cell includes the magnetic memory element 1 of any of the first to fifth embodiments and their modifications, for example, a transistor The switching element 320 which consists of these is provided. The memory cell array 300 includes word lines WL _{1 to} WL _m provided in each row, information read bit lines BL _{1 to} BL _n provided in each column, and items of the first to fifth embodiments. Assist wirings SL _{1 to} SL _n are provided for executing the assist procedure described above. For example, when the magnetic memory element 1 is the first embodiment, the assist wiring SL is a wiring for applying a current magnetic field to the magnetic thin wire 100 in the magnetic memory element 1. In the case where the magnetic memory element 1 is the second embodiment, the assist wiring SL is a wiring for flowing a current that gives a spin torque to the magnetic layer connected to the magnetic wire 100 in the magnetic memory element 1. When the magnetic memory element 1 is the third embodiment, the assist wiring SL is a wiring for applying a current magnetic field to the magnetic layer close to the magnetic wire 100 in the magnetic memory element 1.
In the case where the magnetic memory element 1 is the fourth embodiment, the assist wiring SL is a wiring for flowing a current that gives a spin torque to the magnetic layer connected to the magnetic wire 100 in the magnetic memory element 1. When the magnetic memory element 1 is the fifth embodiment, the assist wiring SL is a wiring that functions as an electrode for applying a voltage to the piezoelectric layer in the vicinity of the magnetic wire 100 in the magnetic memory element 1.

The magnetic memory elements 1 of the n memory cells in the i-th (1 ≦ i ≦ m) row are connected to the magnetic thin wire 100 in common to form the magnetic thin wire ML _i . The magnetic wires 100 of the magnetic memory elements 1 do not have to be connected in common. The switching element 320 of each memory cell has a gate connected to the word line WL _i (1 ≦ i ≦ m) of the corresponding row, and one end connected to one end of the reading unit 120 of the magnetic memory element 1 in the same memory cell. Connected, the other end is grounded. The other end of the read unit 120 of the magnetic memory element 1 in the memory cell is connected to a bit BL _j (1 ≦ j ≦ n) corresponding to the memory cell.

These word lines WL _{1 to} WL _m and magnetic thin lines ML _{1 to} ML _m are connected to drive circuits 410A and 410B having a decoder, a write circuit, and the like for selecting each wiring. Further, the bit lines BL _{1 to} BL _n and the assist lines SL _{1 to} SL _n are connected to the drive circuits 420A and 420B including a decoder for selecting each line, a read circuit, and the like. 27 and 28, the writing unit of the magnetic memory element 1 is omitted and not shown. One end of the writing unit is connected to a switching element for writing selection (not shown), and the other end is connected to a current source (not shown). The writing switching element and the reading switching element may be used in common. Further, one read unit and one write unit may be provided for a plurality of memory cells. In this case, the degree of integration can be increased. Further, as shown in FIGS. 27 and 28, when one read unit and one write unit are provided in each memory cell, the data transfer rate can be increased.

  In the shift movement of data in the memory cell, first, an address signal input from the outside is decoded by a decoder in the drive circuits 410A, 410B, 420A, 420B, and the magnetic thin line ML corresponding to the decoded address is selected. When a current is passed through the selected magnetic wire ML and the magnetic memory element 1 of the memory cell is composed of the magnetic memory element of the first embodiment, for example, a current is supplied to the assist wiring SL at the timing described in the first embodiment. To generate a current magnetic field. When the magnetic memory element 1 is composed of the magnetic memory elements of the second to fifth embodiments, the assist procedure described in the section of each embodiment is executed instead of generating a current magnetic field. The direction in which the domain wall moves is the same as the direction in which electrons flow in the magnetic wire ML, that is, the direction in which the current flows is opposite.

  For writing to the memory cell, first, an address signal inputted from the outside is first decoded by the decoders in the drive circuits 410A, 410B, 420A, 420B, and the word line WL corresponding to the decoded address is selected and corresponding. The switching element 320 is turned on. Next, writing is performed by passing a current through the bit line BL. Alternatively, the data stored in the corresponding magnetic wire ML is moved by a necessary amount, and then writing is performed.

  To read the data stored in the memory cell, first, an address signal input from the outside is first decoded by the decoders in the drive circuits 410A, 410B, 420A, 420B, and the magnetic thin line ML corresponding to the decoded address is selected. In the bit string stored as the magnetization direction in the memory cell, the data shift movement is performed by the above-described method so that the bit to be read is positioned at the reading unit. Thereafter, the word line WL is selected, the switching element 320 is turned on, and a current is passed through the bit line BL to perform reading. Note that the read current may have a positive or negative direction, but has an absolute value smaller than the absolute value of the write current. This is because the data stored by reading is not inverted.

  As shown in FIG. 27 and FIG. 28, the assist wiring SL is parallel to the bit line, but may be arranged to be parallel to the word line or the magnetic thin line ML. In this case, by selecting one distribution SL and executing the assist procedure, the assist procedure is executed for the magnetic memory element 1 in the magnetic wire ML connected to or close to the assist wiring, The shift movement can be simultaneously performed on the plurality of magnetic memory elements 1, and the power consumption of the magnetic memory device can be reduced.

  Throughout this specification, “vertical” includes strict deviation from vertical due to variations in manufacturing processes. Similarly, throughout this specification, “parallel” and “horizontal” do not mean strictly parallel and horizontal.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

1 magnetic storage element 100 magnetic thin wire 101 _{1-101 8} domains 104a, 104b electrode 105 domain wall displacement direction 110 writing unit 112a, 112b electrode 114 nonmagnetic layer 116 magnetization fixed layer 120 reading section 130 magnetic layer 131 magnetized 150 current source 155 current 170 Spin wave generator 172 Magnetic layer 174 Nonmagnetic layer 176 Magnetization fixed layer 177a, 177b Electrode 178 Antiferromagnetic layer 210 Wiring 211 Wiring 212 Wiring 230 Wiring 232 Insulator 240 Spin wave generating portion 242 Magnetic layer 243 Magnetizing 244 Nonmagnetic layer 246 Magnetization fixed layer 247a, 247b Electrode 248 Current source 249 Voltage source 250 Piezoelectric part 252 Piezoelectric layer 254a, 254b Electrode 280, 280A Magnetic storage device 300 Memory cell array 320 Switching element 41 A, 410B driving circuit 420A, 420B drive circuit

Claims (14)

A magnetic wire having a plurality of magnetic domains extending in a first direction and separated by a domain wall;
An electrode capable of flowing a current in the first direction and a current in a direction opposite to the first direction through the magnetic wire;
An assist unit that receives electrical input and assists the movement of the domain wall of the whole or a part of the magnetic wire;
With
The assist unit includes a magnetic layer disposed in the vicinity of at least a part of the magnetic wire, and a wiring for applying a current magnetic field generated when a current flows to the magnetic layer. Magnetic memory element.   The magnetic memory element according to claim 1, wherein the magnetic layer is provided so as to surround at least a part of the magnetic wire. A magnetic wire having a plurality of magnetic domains extending in a first direction and separated by a domain wall;
An electrode capable of flowing a current in the first direction and a current in a direction opposite to the first direction through the magnetic wire;
An assist unit that receives electrical input and assists the movement of the domain wall of the whole or a part of the magnetic wire;
With
The assist unit includes a magnetic layer disposed in the vicinity of at least a part of the magnetic wire, and a coil for applying a current magnetic field generated when a current flows to the magnetic layer. Magnetic memory element.   The magnetic memory element according to claim 3, wherein the magnetic layer is provided so as to surround at least a part of the magnetic wire. A magnetic wire having a plurality of magnetic domains extending in a first direction and separated by a domain wall;
An electrode capable of flowing a current in the first direction and a current in a direction opposite to the first direction through the magnetic wire;
An assist unit that receives electrical input and assists the movement of the domain wall of the whole or a part of the magnetic wire;
With
The assist portion includes a magnetic layer disposed in the vicinity of at least a part of the magnetic wire, a nonmagnetic layer provided on the magnetic layer, and a magnetization direction provided on the nonmagnetic layer. A magnetic memory element comprising: a fixed magnetization fixed layer; and an electrode for passing a current between the magnetic layer and the magnetization fixed layer. A magnetic wire having a plurality of magnetic domains extending in a first direction and separated by a domain wall;
An electrode capable of flowing a current in the first direction and a current in a direction opposite to the first direction through the magnetic wire;
An assist unit that receives electrical input and assists the movement of the domain wall of the whole or a part of the magnetic wire;
With
The assist part is a magnetic memory element comprising: a piezoelectric layer provided so as to surround at least a part of the magnetic wire; and an electrode for applying a voltage to the piezoelectric layer.   The piezoelectric layer is composed of potassium sodium tartrate, zinc oxide, aluminum nitride, lead zirconate titanate, lead lanthanum zirconate titanate, crystal, lithium niobate, lithium tantalate, lithium tetraborate, potassium niobate, langasite The magnetic memory element according to claim 6, comprising any one of a crystal and potassium sodium tartrate tetrahydrate.   The piezoelectric layer is provided on at least one end of the magnetic wire in the first direction, and a substrate is provided in a direction perpendicular to the first direction. The magnetic wire includes Co, CoPt, CoCrPt, and GdFe. The magnetic memory element according to claim 6, comprising any one of GdCo, GdFeCo, TbFe, TbCo, TbFeCo, GdTbFe, GdTbCo, DyFe, DyCo, or DyFeCo.   The piezoelectric layer further includes a substrate that surrounds the magnetic wire in the first direction and is provided on a side opposite to the side on which the magnetic wire is provided of the piezoelectric layer, wherein the magnetic wire is a Co layer And a Ni layer, or any one of Co, CoPt, FePt, GdFe, GdCo, GdFeCo, TbFe, TbCo, TbFeCo, GdTbFe, GdTbCo, DyFe, DyCo, or DyFeCo. Magnetic storage element. A plurality of magnetic wires each having a plurality of magnetic domains extending in the first direction and separated by a domain wall;
A piezoelectric layer provided to surround each magnetic wire;
An electrode provided along the first direction for applying a voltage to the piezoelectric layer;
A magnetic storage device. A plurality of magnetic wires arranged in a matrix, each of which has a plurality of magnetic domains extending in the first direction and separated by a domain wall;
A plurality of first wires provided on one of the upper surface and the lower surface of the plurality of magnetic wires corresponding to the row of the plurality of magnetic wires;
A plurality of second wires provided on the one surface of the plurality of magnetic wires corresponding to the plurality of rows of the magnetic wires;
A piezoelectric layer provided along a plane orthogonal to the first direction;
An electrode provided along a plane orthogonal to the first direction for applying a voltage to the piezoelectric layer;
A magnetic storage device.   The magnetic storage device according to claim 11, wherein the piezoelectric layer and the electrode are provided on the same side as the one of the upper and lower surfaces of the plurality of magnetic thin wires.   The magnetic storage device according to claim 11, wherein the piezoelectric layer and the electrode are provided on a surface opposite to the one surface among the upper and lower surfaces of the plurality of magnetic thin wires.   A magnetic memory comprising a plurality of magnetic storage devices according to claim 10, wherein the plurality of magnetic storage devices are arranged in a matrix.