CN119110667A - A magnetic memory based on electric field regulation of exchange bias field - Google Patents

Abstract

The application provides a magnetic memory based on an electric field regulation exchange bias field, which relates to the field of magnetic memories and comprises an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer which are sequentially attached from bottom to top, wherein the insulating insertion layer keeps the exchange bias field generated between the antiferromagnetic layer and the free layer, when longitudinal voltage is applied to the insulating insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is overturned, and the magnetic moment of the free layer is overturned, so that information writing is realized. The application can regulate and control the states of atoms or ions at the upper and lower interfaces of the insulating insertion layer through an electric field, and change the magnetic neighbor effect, thereby leading the exchange bias field to change in size and direction and driving the free layer to realize information writing.

Description

Magnetic memory based on electric field regulation and control exchange bias field

Technical Field

The application relates to the field of magnetic memories, in particular to a magnetic memory based on an electric field regulation exchange bias field.

Background

The magnetic random access memory (Magnetic Random Access Memory, abbreviated as MRAM) has the characteristics of high speed, non-volatile, compatibility with CMOS technology and the like, and has important application prospect in the storage field. The basic unit magnetic tunnel junction (Magnetic Tunnel Junction, abbreviated as MTJ) is a tunneling magnetoresistance (Tunneling Magnetoresistance, abbreviated as TMR) device composed of a free layer (ferromagnetic layer)/insulating layer (tunneling layer, barrier layer)/reference layer (ferromagnetic layer) sandwich structure, and the magnetic moment of the free layer is parallel (antiparallel) to the magnetic moment of the reference layer, so that the device has a low resistance state (high resistance state) and becomes the basis of information storage.

In pursuit of the capacity of the magnetic random access memory, it is necessary to miniaturize the size of the magnetic tunnel junction as much as possible, however, when the device size is miniaturized to within hundred nanometers, it is difficult to maintain sufficient thermal stability of the in-plane magnetic tunnel junction by virtue of shape anisotropy. Subsequently, the introduction of perpendicular magnetic anisotropy makes the thermal stability of the magnetic tunnel junction no longer dependent on shape anisotropy, but can be maintained by perpendicular magnetic anisotropy. However, as the magnetic tunnel junction size is further scaled down, the interface perpendicular magnetic anisotropy strength is also difficult to maintain sufficiently high thermal stability, and to solve this problem, a exchange bias field is introduced into the magnetic tunnel junction, the free layer is stabilized in one direction by virtue of the exchange bias field generated by the antiferromagnetic and ferromagnetic interface, and the thermal stability of the free layer is no longer dependent solely on the shape anisotropy and interface perpendicular magnetic anisotropy, but rather depends on the exchange bias field of the antiferromagnetic/ferromagnetic interface. It is the antiferromagnetic that has a high degree of stability that makes such exchange bias based magnetic tunnel junctions have the potential for further device scaling. However, such exchange bias-based magnetic tunnel junctions require extremely high current densities to change the exchange bias field direction by means of spin-orbit torque or thermal effects, which is detrimental to the wide range of device applications.

The latest scientific research shows that not only the spin orbit distance current can turn over the exchange bias field, but also the electric field is an effective way to regulate the exchange bias field, and has unique advantages in the aspect of writing power consumption. Wherein the electric field can change the state of the antiferromagnetic and ferromagnetic interface at the interface by adjusting the movement of atoms or ions, thereby changing the magnitude and direction of the exchange bias field. In addition, the electric field can also change the coupling strength of the ferromagnetic and antiferromagnetic layers through the movement of atoms or ions and the magnetic neighbor effect, hopefully realizing the change of the exchange bias field. And an electric field regulation mechanism is introduced into a magnetic tunnel junction based on exchange bias to solve the problems of high current density and writing power consumption, and the method has important significance for promoting the development of a spin electronic device in the fields of ultra-low power consumption storage and calculation.

Disclosure of Invention

Aiming at the problems in the prior art, the application provides a magnetic memory based on an electric field regulation exchange bias field, which can change the magnetic neighbor effect by regulating the states of atoms or ions at the upper interface and the lower interface of an insulating insertion layer through the electric field, so that the exchange bias field is changed in size and direction, and a free layer is driven to realize information writing.

In order to solve the technical problems, the application provides the following technical scheme:

The application provides a magnetic memory based on an electric field regulation exchange bias field, which comprises an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer which are sequentially attached from bottom to top, wherein the insulating insertion layer keeps the exchange bias field generated between the antiferromagnetic layer and the free layer, when a longitudinal voltage is applied to the insulating insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is turned over, and the magnetic moment of the free layer is turned over, so that information writing is realized.

Further, the antiferromagnetic layer is made of one or any combination of platinum manganese, iridium manganese, palladium manganese and iron manganese.

Further, the antiferromagnetic layer has a thickness of 1nm to 10nm.

Further, the material of the insulating insertion layer is one or any combination of gadolinium oxide, aluminum oxide and magnesium oxide, and the component number of oxygen in the gadolinium oxide, the aluminum oxide or the magnesium oxide is 0.1-3.

Further, the thickness of the insulating interposed layer is 0.2nm to 4nm.

Further, the free layer is made of ferromagnetic material, wherein the magnetization direction of the ferromagnetic material can be reversed, and the coercive field of the free layer is smaller than the exchange bias field.

Further, the material of the barrier layer is magnesia, and the thickness is 0.6nm to 2nm.

Further, the fixed layer is a ferromagnetic material, wherein the coercive field of the fixed layer is higher than that of the free layer.

Further, a heavy metal layer is arranged at the bottom of the antiferromagnetic layer, and the heavy metal layer is used for realizing the change of the exchange bias field by utilizing the longitudinal voltage and realizing the inversion of the exchange bias field by utilizing spin orbit moment inversion antiferromagnetic magnetic moment generated by transverse current in heavy metal.

Further, one end of the free layer is provided with an electrode so that the information writing voltage is distributed only on both sides of the insulating interposed layer, not on the barrier layer.

The magnetic memory based on the electric field regulation exchange bias field can realize high tunneling magnetic resistance through optimizing materials and processes to ensure the accuracy of information reading in application, and can control the magnetic moment direction of the free layer because the exchange bias field between the antiferromagnetic layer and the free layer is larger than the coercive field of the free layer, so that the antiferromagnetic layer magnetic sequence is related to the ferromagnetic layer magnetic sequence, and meanwhile, the stability of the magnetic moment of the free layer is greatly improved because the thickness and the materials of the antiferromagnetic layer are regulated, in addition, the exchange bias field between the antiferromagnetic layer and the free layer is still larger than the coercive field of the free layer, and the state of atoms or ions at the upper interface and the lower interface of the insulating insertion layer can be regulated through the electric field, so that the magnetic neighbor effect is changed, the exchange bias field is changed in size and direction, and the free layer is driven to realize information writing.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a block diagram of a magnetic memory based on electric field modulated exchange bias fields in an embodiment of the application.

FIG. 2 is a diagram of one of the improved structures of a magnetic memory based on electric field modulated exchange bias fields in an embodiment of the present application.

FIG. 3 is a schematic diagram of a magnetic tunnel junction high density memory mode based on electric field and spin-orbit torque modulation exchange bias field in an embodiment of the application.

FIG. 4 is a diagram showing a second embodiment of a magnetic memory based on an electric field controlled exchange bias field.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

In one embodiment, referring to fig. 1, in order to change the magnetic neighbor effect by regulating and controlling the states of atoms or ions at the upper and lower interfaces of an insulating insertion layer through an electric field, so that the exchange bias field changes in size and direction and drives a free layer to realize information writing, the application provides a magnetic memory based on the electric field regulating and controlling the exchange bias field.

It will be appreciated that the magnetic memory based on electric field modulated exchange bias field of the present invention is a spintronic device comprising five layers, from bottom to top, an antiferromagnetic layer, an insulating interlayer, a free layer, a barrier layer, and a fixed layer, respectively, as shown in FIG. 1. The extremely thin insulating insertion layer is positioned between the free layer and the antiferromagnetic layer, so that the original exchange bias field between the antiferromagnetic layer and the free layer can be maintained to a certain extent, meanwhile, when a certain longitudinal voltage is applied to the device, a stronger longitudinal electric field can be formed between the free layer and the antiferromagnetic layer, and the offset of atoms or ions is caused, so that the magnetic neighbor effect is changed, the exchange bias field is turned over, the magnetic moment of the free layer is driven to be turned over, and information writing is realized. FIG. 1 is a schematic diagram of a magnetic tunnel junction structure based on electric field modulation exchange bias field.

E is the electric field in the vertical direction.

In one embodiment, the antiferromagnetic layer is made of one or any combination of platinum manganese, iridium manganese, palladium manganese and iron manganese.

In one embodiment, the antiferromagnetic layer has a thickness of 1nm (nanometer) to 10nm (nanometer).

It is understood that the antiferromagnetic layer is one or any two, three or four of platinum manganese (PtMn), iridium manganese (IrMn), palladium manganese (PdMn) and iron manganese (FeMn), and the thickness can be 1nm (nanometer) to 10nm (nanometer). The common element proportion of PtMn can be Pt ₅₀Mn₅₀、Pt₂₀Mn₈₀、Pt₂₅Mn₇₅, pt ₇₅Mn₂₅ or the like, the common element proportion of IrMn can be Ir ₅₀Mn₅₀、Ir₂₀Mn₈₀, ir ₂₅Mn₇₅ or the like, the common element proportion of PdMn can be Pd ₅₀Mn₅₀、Pd₉₀Mn₁₀, pd ₇₅Mn₂₅ or the like, the common element proportion of FeMn can be Fe ₅₀Mn₅₀, fe ₈₀Mn₂₀ or the like, and the numbers in the materials represent the percentages of elements. In addition, the material of the antiferromagnetic layer may be one or any combination of nickel oxide (NiO), ruthenium oxide (RuO _x), chromium oxide (Cr ₂O₃), iridium manganese oxide (YMnO ₃), bismuth iron oxide (BiFeO 3). The value of x in the material can be 0.1-3, and the thickness of the antiferromagnetic layer can be 3nm (nanometers) to 100nm (nanometers). The antiferromagnetic layer based on the material has higher thermal stability, and can still keep stable antiferromagnetic magnetic sequence and external magnetic resistance at normal temperature. Through selection and optimization of the substrate, the antiferromagnetic material has good monocrystal characteristics and relatively consistent magnetic moment orientation, so that a relatively large exchange bias field can be provided for a neighboring (ferromagnetic) free layer, so that the coercive field of the (ferromagnetic) free layer is larger than that of the (ferromagnetic) free layer, and further, the magnetic moment direction of the (ferromagnetic) free layer is completely controlled through the exchange bias field, and a foundation is laid for a subsequent voltage-controlled exchange bias field writing mode.

In one embodiment, the material of the insulating insertion layer is one or any combination of gadolinium oxide, aluminum oxide and magnesium oxide, and the component number of oxygen in gadolinium oxide, aluminum oxide or magnesium oxide is 0.1-3.

In one embodiment, the thickness of the insulating interposed layer is 0.2nm to 4nm.

It is understood that the insulating insertion layer is one or a combination of any two or three of gadolinium oxide (GdO _x), aluminum oxide (AlO _x) and magnesium oxide (MgO _x). The x value in the material can be 0.1-3, and the thickness of the insulating insertion layer can be 0.2nm (nanometer) to 4nm (nanometer). Different metals and the ratio of the metals to oxygen elements can influence the magnetic neighbor effect of the insulating insertion layer and the equivalent thickness of the insulating insertion layer, and can also influence the efficiency of the voltage regulation exchange bias field. The element proportion and thickness of the interval are reasonably selected, so that a sufficient exchange bias field value can be ensured between the (ferromagnetic) free layer and the antiferromagnetic layer, and meanwhile, the direction switching of the exchange bias field between the antiferromagnetic layer and the (ferromagnetic) free layer can be regulated and controlled through voltage, so that the state of the ferromagnetic free layer is written.

In addition, the insulating insertion layer can effectively avoid element migration in the antiferromagnetic material at high temperature, so that the applicable annealing temperature is improved, and the performance of the whole device is improved. Further, exchange bias field switching controlled by the electric field can be achieved by inserting a specific insulating insertion layer between the antiferromagnetic layer and the (ferromagnetic) free layer. Further, the insulating interlayer may also limit elemental diffusion during high temperature annealing.

In one embodiment, the free layer is a ferromagnetic material, wherein the magnetization direction of the ferromagnetic material can be reversed and the coercive field of the free layer is less than the exchange bias field.

It will be appreciated that the free layer is a ferromagnetic material whose magnetization direction can be reversed and whose coercive field is smaller than the exchange bias field. For example, a simple metal including only one of chromium (Cr), manganese (Mn), cobalt (Co), iron (Fe), and nickel (Ni), a metal alloy containing one or more of the above five metals and exhibiting ferromagnetism, or an alloy containing at least one or more of the above metals and the following elements (boron (B), carbon (C), and nitrogen (N)) may be used as the material of the free layer. Specifically, for example, co-Fe-B, ni-Fe, coNi, coPt, etc.

In the writing mode, since the exchange bias field formed with the antiferromagnetic layer is larger than the coercive field of the magnetic layer, the magnetic moment direction of the (ferromagnetic) free layer can be completely determined by the exchange bias field, and information writing to the (ferromagnetic) free layer is realized by the voltage-controlled exchange bias field. In information reading, the sandwich structure formed by the (ferromagnetic) free layer, the barrier layer and the fixed layer can generate stronger tunneling magnetic resistance effect, has higher tunneling magnetic resistance rate and is convenient for reading the high-low resistance state of the device.

In one embodiment, the material of the barrier layer is magnesium oxide, and the thickness of the barrier layer is 0.6nm (nanometer) to 2nm (nanometer). It is understood that the material of the barrier layer is magnesium oxide (MgO). The barrier layers in magnetic tunnel junction layers with higher tunneling magnetoresistance in the current industry are all magnesium oxide (MgO). Due to its relatively uniform lattice structure, the tunneling magnetoresistance effect may be enhanced.

In an embodiment, the fixed layer is a ferromagnetic material, wherein the coercive field of the fixed layer is higher than the coercive field of the free layer.

It will be appreciated that the material of the fixed layer is a ferromagnetic (composite) material that has a coercive field that is much higher than that of the free layer. The ferromagnetic (composite) material may be artificially synthesized. For example, an elemental metal including only one of chromium (Cr), manganese (Mn), cobalt (Co), iron (Fe), and nickel (Ni), a metal alloy containing one or more of the above five metals and exhibiting ferromagnetism, or an alloy containing at least one of the above metals and the following elements (boron (B), carbon (C), and nitrogen (N)) may be used for the fixing layer. Specifically, for example, co-Fe-B, ni-Fe, coNi, coPt may be formed as a single-layer film or a multi-layer film of the above alloy.

In an embodiment, a heavy metal layer is disposed at the bottom of the antiferromagnetic layer, and is used for changing the exchange bias field by using the longitudinal voltage, and reversing antiferromagnetic magnetic moment by using spin orbit moment generated by transverse current in heavy metal, so as to achieve reversing of the exchange bias field.

It will be appreciated that based on the basic structure shown in fig. 1, heavy metals may be added to the bottom of the antiferromagnetic layer, so that either the change of the exchange bias field may be achieved by using the longitudinal voltage, or the spin-orbit moment generated by the transverse current in the heavy metals may be used to flip the antiferromagnetic magnetic moment, so as to achieve the flip of the exchange bias field, as shown in fig. 2. The structure can be used for exploring the synergic action of two exchange bias field inversions to construct a three-port device, and further has an application prospect in the NAND-SPIN high-density storage field, as shown in figure 3. Wherein FIG. 2 is a schematic diagram of a magnetic tunnel junction based on electric field and spin-orbit torque modulation exchange bias field. FIG. 3 is a schematic diagram of a magnetic tunnel junction high density memory mode based on electric field and spin-orbit torque modulation exchange bias field.

In one embodiment, an electrode is disposed at one end of the free layer, so that the information writing voltage is distributed only on two sides of the insulating interposed layer, and is not distributed on the barrier layer.

It will be appreciated that based on the basic structure shown in fig. 1, additional electrodes may be provided at the (ferromagnetic) free layer such that the write voltage is distributed only on both sides of the insulating interposed layer and not on the barrier layer. This arrangement is advantageous for protecting the barrier layer and thus increasing the lifetime of the device, and also for further reducing the write voltage, the specific device configuration being shown in fig. 4. Wherein FIG. 4 is a schematic diagram of a magnetic tunnel junction structure based on an electric field modulated exchange bias field with efficient writing characteristics.

In summary, the invention has at least the following advantages:

first, the insulating interlayer is capable of providing a large electric field strength between the antiferromagnetic layer and the ferromagnetic (free) layer, such that the exchange bias field is flipped under atomic or ion movement and magnetic nearest neighbor effects. On one hand, the scheme utilizes voltage to regulate magnetic neighbor effect at the interface of the antiferromagnetic/insulating insertion layer and the insulating insertion layer/(ferromagnetic) free layer to realize the change of the direction of the exchange bias field, so that only the interface property is required to be changed, the internal structure of the film layer is not required to be changed, the required voltage is small and the method is easy to be compatible with a CMOS (complementary metal oxide semiconductor) process, and on the other hand, the writing mode is voltage effect writing, does not need current and has ultralow power consumption property.

Second, the insulating insert layer can well avoid element diffusion at high temperature, is favorable for raising annealing temperature, and is compatible with CMOS back-end process.

As can be seen from the above description, the magnetic memory based on the electric field regulation exchange bias field provided by the application has the advantages that the fixed layer, the barrier layer and the free layer can realize high tunneling magnetoresistance through optimizing materials and processes so as to ensure the accuracy of information reading in application, the exchange bias field between the antiferromagnetic layer and the free layer is larger than the coercive field of the free layer, so that the magnetic moment direction of the free layer can be controlled, the antiferromagnetic layer magnetic sequence is related to the ferromagnetic layer magnetic sequence, meanwhile, the stability of the magnetic moment of the free layer is greatly improved due to the high stability of the antiferromagnetic layer, in addition, the exchange bias field between the antiferromagnetic layer and the free layer can be still larger than the coercive field of the free layer through regulating the thickness and materials of the insulating insertion layer, and the atomic or ionic state of the upper interface and the lower interface of the insulating insertion layer can be regulated through the electric field, the magnetic neighbor effect is changed, the change of the exchange bias field is caused to cause the change in size and direction, and the free layer is driven to realize information writing.

In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments.

The foregoing describes specific embodiments of the present disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the embodiments of the present specification. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

The foregoing is merely an example of an embodiment of the present disclosure and is not intended to limit the embodiment of the present disclosure. Various modifications and variations of the illustrative embodiments will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, or the like, which is within the spirit and principles of the embodiments of the present specification, should be included in the scope of the claims of the embodiments of the present specification.

Claims (10)

1. A magnetic memory based on an electric field regulation exchange bias field is characterized by comprising an antiferromagnetic layer, an insulating insertion layer, a free layer, a barrier layer and a fixed layer which are sequentially attached from bottom to top, wherein the insulating insertion layer keeps the exchange bias field generated between the antiferromagnetic layer and the free layer, when a longitudinal voltage is applied to the insulating insertion layer, a longitudinal electric field is formed between the free layer and the antiferromagnetic layer, the exchange bias field is turned over, and the magnetic moment of the free layer is turned over, so that information writing is realized.

2. The magnetic memory based on electric field regulated exchange bias field according to claim 1, wherein the antiferromagnetic layer is made of one or any combination of platinum manganese, iridium manganese, palladium manganese, and iron manganese.

3. The magnetic memory based on electric field modulated exchange bias field according to claim 1, wherein the thickness of the antiferromagnetic layer is 1nm to 10nm.

4. The magnetic memory based on the electric field regulation exchange bias field according to claim 1, wherein the material of the insulating insertion layer is one or any combination of gadolinium oxide, aluminum oxide and magnesium oxide, and the component of oxygen in the gadolinium oxide, the aluminum oxide or the magnesium oxide is 0.1 to 3.

5. The magnetic memory based on electric field modulated exchange bias field of claim 4, wherein the thickness of said insulating interposed layer is 0.2nm to 4nm.

6. The magnetic memory of claim 1 wherein the free layer is a ferromagnetic material, wherein the magnetization direction of the ferromagnetic material can be reversed and the coercive field of the free layer is less than the exchange bias field.

7. The magnetic memory based on electric field controlled exchange bias field according to claim 1, wherein the material of the barrier layer is magnesium oxide with a thickness of 0.6nm to 2nm.

8. The magnetic memory of claim 1 wherein the fixed layer is a ferromagnetic material and wherein the coercive field of the fixed layer is higher than the coercive field of the free layer.

9. The magnetic memory based on electric field regulation exchange bias field according to claim 1, wherein a heavy metal layer is arranged at the bottom of the antiferromagnetic layer for realizing the change of the exchange bias field by using the longitudinal voltage and the inversion of the exchange bias field by using spin-orbit moment inversion antiferromagnetic magnetic moment generated by a transverse current in heavy metal.

10. The magnetic memory based on electric field controlled exchange bias field according to claim 1, wherein one end of said free layer is provided with an electrode so that information writing voltage is distributed only on both sides of said insulating interposed layer, not on said barrier layer.