CN119152902A - Magnetic memory cell and SOT-MRAM memory - Google Patents
Magnetic memory cell and SOT-MRAM memory Download PDFInfo
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- 230000005291 magnetic effect Effects 0.000 title claims abstract description 368
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- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
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- 239000002885 antiferromagnetic material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- H—ELECTRICITY
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- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
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- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
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- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
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Abstract
本发明公开了一种磁存储单元及SOT‑MRAM存储器，应用于MRAM存储器技术领域，包括至少一组差分位元和辅助磁结构；差分位元包括：自旋轨道矩提供线；位于自旋轨道矩提供线一侧的两个磁性隧道结；差分位元具有平行于自旋轨道矩提供线轴线的第一方向，和与第一方向垂直的初始磁化方向；辅助磁结构对同一差分位元中的两个磁性隧道结分别提供偏置磁场，偏置磁场具有沿第一方向的分量，和沿初始磁化方向的分量；两偏置磁场沿初始磁化方向的分量方向相同，两偏置磁场沿第一方向的分量方向相反。仅需要受到沿初始磁化方向的一次初始磁化，就可以完成初始化，同时解决垂直磁化的MTJ零磁场的可靠写入问题和高速读取问题。
The present invention discloses a magnetic storage unit and SOT-MRAM memory, which are applied to the field of MRAM memory technology, and include at least one group of differential bits and an auxiliary magnetic structure; the differential bit includes: a spin-orbit moment providing line; two magnetic tunnel junctions located on one side of the spin-orbit moment providing line; the differential bit has a first direction parallel to the axis of the spin-orbit moment providing line, and an initial magnetization direction perpendicular to the first direction; the auxiliary magnetic structure provides a bias magnetic field to the two magnetic tunnel junctions in the same differential bit, respectively, and the bias magnetic field has a component along the first direction and a component along the initial magnetization direction; the components of the two bias magnetic fields along the initial magnetization direction are in the same direction, and the components of the two bias magnetic fields along the first direction are in opposite directions. Only one initial magnetization along the initial magnetization direction is required to complete the initialization, and at the same time, the reliable writing problem and high-speed reading problem of the perpendicularly magnetized MTJ zero magnetic field are solved.
Description
Technical Field
The present invention relates to the field of MRAM memory technologies, and in particular, to a magnetic memory cell and an SOT-MRAM memory.
Background
SOT-MTJ (spin-orbit torque magnetic tunnel junction ) devices are one of the core structure types of MRAM (Magnetoresistive Random Access Memory, magnetic random access memory) products, and compared with STT-MTJ (SPIN TRANSFER Torque magnetic tunnel junction, spin-transfer torque magnetic tunnel junction) devices, SOT-MTJ devices have the characteristics of fast writing speed, unlimited erasing and read-write separation. The SOT-MTJ device has two obvious structural characteristics that an SOT (spin-orbit) track layer provides an independent channel for write current and is separated from read and write, and secondly, a horizontal magnetic field needs to be applied along the current direction to realize the deterministic inversion of a vertical free layer, and the inversion polarity depends on the relative direction of the horizontal magnetic field and the current acting on the free layer.
In the traditional SOT-MRAM (spin-orbit torque Magnetoresistive Random Access Memory, spin-orbit torque magnetic random access memory) manufacture, the MTJ (magnetic tunnel junction ) adopts a top-pinned structure, the integration of spin-orbit torque material and high TMR (Tunnel Magneto Resistance, tunneling magnetic resistance) material is difficult, the TMR ratio is generally not high, only about 100% can be achieved at present, the reading and writing speed of the SOT-MRAM is directly influenced, and the differential bit is an effective solution to the problem. In the prior art, however, the auxiliary magnetic layer needs to be initially magnetized twice, and the auxiliary magnetic layer obtains different switching magnetic fields by adopting different aspect ratios, so that the operation window is limited. It is an urgent problem for those skilled in the art to provide a reliable, simple to operate, high speed readable and writable SOT-MRAM memory.
Disclosure of Invention
The invention aims to provide a vertical magnetization-based SOT-MRAM differential bit design scheme which can simultaneously solve the problem of reliable writing of a zero magnetic field and the problem of high-speed reading.
In order to solve the above technical problems, the present invention provides a magnetic memory cell, which includes at least one group of differential bits and an auxiliary magnetic structure, wherein the differential bits include:
Spin orbit torque providing lines;
The differential bit has a first direction parallel to the spin-orbit-torque-providing line axis and an initial magnetization direction perpendicular to the first direction;
the auxiliary magnetic structure provides bias magnetic fields for two magnetic tunnel junctions in the same differential bit, the bias magnetic fields have components along the first direction and components along the initial magnetization direction, the component directions of the two bias magnetic fields along the initial magnetization direction are the same, and the component directions of the two bias magnetic fields along the first direction are opposite.
Optionally, a separation layer is disposed on a surface of the magnetic tunnel junction on a side facing away from the spin orbit torque providing line;
The auxiliary magnetic structure comprises an auxiliary magnetic layer which is positioned on the surface of one side of the separation layer, which is opposite to the spin orbit torque providing line, and is provided with an in-plane easy axis, wherein magnetic moments of the auxiliary magnetic layer and the first direction form an included angle, so that component directions of magnetic moments of two auxiliary magnetic layers corresponding to the same differential bit along the first direction are opposite, component directions along a second direction are the same, and the second direction is a direction perpendicular to the first direction in a horizontal plane.
Optionally, the included angles corresponding to the two auxiliary magnetic layers corresponding to the same differential bit are complementary angles.
Optionally, the range of the included angle between one auxiliary magnetic layer corresponding to the same differential bit and the first direction is 20 ° to 70 °, including the end point value, and the range of the included angle between the other auxiliary magnetic layer and the first direction is 110 ° to 160 °, including the end point value.
Optionally, the auxiliary magnetic structure further comprises a pinning layer located on a side surface of the auxiliary magnetic layer facing away from the spin orbit torque providing line, and the magnetic moment direction of the pinning layer corresponds to the magnetic moment direction of the contacted auxiliary magnetic layer.
Optionally, the auxiliary magnetic structure includes an auxiliary magnetic body, and one auxiliary magnetic body provides the bias magnetic field to two magnetic tunnel junctions in the same differential bit.
Optionally, the auxiliary magnetic body is located on a side of the spin-orbit torque providing line facing away from the magnetic tunnel junction, and the auxiliary magnetic body has perpendicular magnetic anisotropy.
Optionally, the auxiliary magnetic body is located at an intermediate position of two magnetic tunnel junctions of the same differential bit.
Optionally, the magnetic tunnel junction comprises two groups of differential bits, the spin orbit moments of the two groups of differential bits provide line parallelism, the auxiliary magnetic body is located between the two groups of differential bits, and one auxiliary magnetic body provides the bias magnetic field for the two groups of differential bits, and the four magnetic tunnel junctions are all four.
The invention also provides an SOT-MRAM memory comprising a magnetic memory cell as defined in any one of the preceding claims.
The invention provides a magnetic memory cell, which comprises at least one group of differential bit and an auxiliary magnetic structure, wherein the differential bit comprises a spin orbit moment providing line, two magnetic tunnel junctions positioned at one side of the spin orbit moment providing line, the differential bit is provided with a first direction parallel to the axis of the spin orbit moment providing line and an initial magnetization direction perpendicular to the first direction, the auxiliary magnetic structure respectively provides bias magnetic fields for the two magnetic tunnel junctions in the same differential bit, the bias magnetic fields are provided with components along the first direction and components along the initial magnetization direction, the component directions of the two bias magnetic fields along the initial magnetization direction are the same, and the component directions of the two bias magnetic fields along the first direction are opposite.
Since the bias magnetic field provided by the auxiliary magnetic structure to the magnetic tunnel junctions has components in the first direction and the initial magnetization direction, the components of the bias magnetic field along the first direction are opposite, and the components along the initial magnetization direction are the same in the two magnetic tunnel junctions in the same differential bit. Therefore, the initial magnetization along the initial magnetization direction is only needed to be carried out once, so that the directions of the horizontal components of the free layers of the two magnetic tunnel junctions are opposite to each other, the initialization is completed, and the problem of reliable writing and the problem of high-speed reading of the perpendicular magnetization MTJ zero magnetic field are solved.
The invention also provides an SOT-MRAM memory, which has the same beneficial effects and is not described herein.
Drawings
For a clearer description of embodiments of the invention or of the prior art, the drawings that are used in the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a magnetic memory cell according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a first specific magnetic memory cell according to an embodiment of the present invention;
FIG. 3 is a schematic top view of FIG. 2;
FIG. 4 is a schematic diagram of a second embodiment of a magnetic memory cell according to the present invention;
FIG. 5 is a schematic diagram of a third embodiment of a magnetic memory cell according to the present invention;
FIG. 6 is a schematic diagram of a fourth embodiment of a magnetic memory cell according to the present invention;
Fig. 7 is a schematic side view of fig. 6.
In the figure, 1 is a spin-orbit torque providing line, 2 is a magnetic tunnel junction, 21 is a free layer, 22 is a barrier layer, 23 is a fixed layer, 24 is a separation layer, 3 is an auxiliary magnetic structure, 31 is an auxiliary magnetic layer, 32 is a pinning layer, and 33 is an auxiliary magnetic body.
Detailed Description
The core of the invention is to provide a magnetic memory cell. In the prior art, the SOT-MRAM device based on differential bit needs to perform initial magnetization twice before writing information, and the auxiliary magnetic layer obtains different turning magnetic fields by adopting different length-width ratios, so that the operation window is limited.
The invention provides a magnetic memory cell, which comprises at least one group of differential bit and an auxiliary magnetic structure, wherein the differential bit comprises a spin orbit moment providing line, two magnetic tunnel junctions positioned at one side of the spin orbit moment providing line, the differential bit is provided with a first direction parallel to the axis of the spin orbit moment providing line and an initial magnetization direction perpendicular to the first direction, the auxiliary magnetic structure respectively provides bias magnetic fields for the two magnetic tunnel junctions in the same differential bit, the bias magnetic fields are provided with components along the first direction and components along the initial magnetization direction, the component directions of the two bias magnetic fields along the initial magnetization direction are the same, and the component directions of the two bias magnetic fields along the first direction are opposite.
Since the bias magnetic field provided by the auxiliary magnetic structure to the magnetic tunnel junctions has components in the first direction and the initial magnetization direction, the components of the bias magnetic field along the first direction are opposite, and the components along the initial magnetization direction are the same in the two magnetic tunnel junctions in the same differential bit. Therefore, the initial magnetization along the initial magnetization direction is only needed to be carried out once, so that the directions of the horizontal components of the free layers of the two magnetic tunnel junctions are opposite to each other, the initialization is completed, and the problem of reliable writing and the problem of high-speed reading of the perpendicular magnetization MTJ zero magnetic field are solved.
In order to better understand the aspects of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and detailed description. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a magnetic memory cell according to an embodiment of the invention.
Referring to fig. 1, in an embodiment of the present invention, a magnetic memory cell includes at least one set of differential bits and an auxiliary magnetic structure 3, the differential bits include a spin-orbit torque providing line 1, two magnetic tunnel junctions 2 located at one side of the spin-orbit torque providing line 1, the magnetic tunnel junctions 2 include a free layer 21, a barrier layer 22, and a fixed layer 23 sequentially disposed in a direction from a surface of the spin-orbit torque providing line 1 to a side away from the spin-orbit torque providing line 1, the differential bits have a first direction parallel to an axis of the spin-orbit torque providing line 1 and an initial magnetization direction perpendicular to the first direction, the auxiliary magnetic structure 3 provides bias magnetic fields having components in the first direction and components in the initial magnetization direction to the two magnetic tunnel junctions 2 in the same differential bits, the component directions of the bias magnetic fields in the initial magnetization direction are the same, and the component directions of the bias magnetic fields in the first direction are opposite.
The above differential bit is a basic unit for storing a differential signal, and includes a spin-orbit torque supply line 1, and two magnetic tunnel junctions 2 located on one side of the spin-orbit torque supply line 1. The above-described spin torque supply line, i.e., the SOT supply line, the current flowing through the spin torque supply line 1 can induce a torque to drive magnetization inversion of the free layer 21. The material of the spin-orbit torque providing wire 1 described above needs to be a material having a spin-orbit torque effect, including heavy metals, biSe alloys, antiferromagnetic or two-dimensional materials, and the like. The specific material for the spin orbit torque providing line 1 is not particularly limited herein.
Two magnetic tunnel junctions 2 are provided on one side of the spin orbit torque supply line 1 to constitute a differential bit. Two magnetic tunnel junctions 2 in one differential bit need to write opposite information when writing data. The magnetic tunnel junction 2 includes a free layer 21, a barrier layer 22, and a fixed layer 23 which are sequentially provided in a direction from the surface of the spin-orbit torque supply line 1 to a side away from the spin-orbit torque supply line 1, that is, the free layer 21 of the magnetic tunnel junction 2 is provided near the spin-orbit torque supply line 1, and the fixed layer 23 is provided away from the spin-orbit torque supply line 1. The specific structure of the magnetic tunnel junction 2 may be referred to in the prior art, and will not be described herein.
The two obvious structural features of the SOT-MTJ device are that the SOT track layer provides an independent channel for the write current, the read and write are separated, and secondly, a horizontal magnetic field needs to be applied along the current direction to achieve deterministic inversion of the vertical free layer 21, and the inversion polarity depends on the relative direction of the horizontal magnetic field and the current acting on the free layer 21. Accordingly, in the present embodiment, the magnetic field direction of the free layer 21 and the fixed layer 23 in the magnetic tunnel junction 2 is a perpendicular direction, that is, in the present embodiment, the magnetic tunnel junction 2 is specifically a perpendicular magnetization MTJ, and the reference layer of the magnetic tunnel junction 2 is perpendicular magnetized. In the present embodiment, a direction parallel to the axis of the spin-orbit torque providing line 1 is defined as a first direction, and a direction of a magnetic field applied at the time of initialization is defined as an initial magnetization direction which is perpendicular to the first direction, and may be perpendicular to the first direction in a horizontal plane or perpendicular to the first direction in a vertical plane.
In this embodiment, an auxiliary magnetic structure 3 is further provided, and the auxiliary magnetic structure 3 applies magnetic fields in different directions, i.e. bias magnetic fields, to the two magnetic tunnel junctions 2 in one differential bit. It is necessary for each magnetic tunnel junction 2 to be subjected to a bias magnetic field having a component in the first direction and a component in the initial magnetization direction. For a differential bit, the bias magnetic fields respectively applied to the two magnetic tunnel junctions 2 need to have the same component direction along the initial magnetization direction and opposite component directions along the first direction. Typically, the bias magnetic field experienced by two magnetic tunnel junctions 2 in a differential bit cell needs to be substantially equal in magnitude along the first direction.
In the initialization process, after the initialization of the external magnetic field along the initial magnetization direction, the auxiliary magnetic structure 3 realizes the opposite directions of the components of the magnetic fields applied by the two magnetic tunnel junctions 2 along the first direction in the same differential bit, so that the directions of the stray fields received by the free layers 21 in the magnetic tunnel junctions 2 are opposite. When a current is passed in the spin-orbit torque supply line 1, the two free layers 21 will be written in opposite directions, thereby realizing the storage of differential information.
The details of the auxiliary magnetic structure 3 will be described in detail in the following embodiments of the present invention, and will not be described herein.
In the magnetic memory unit provided by the embodiment of the invention, the bias magnetic field provided by the auxiliary magnetic structure 3 to the magnetic tunnel junctions 2 has components in the first direction and the initial magnetization direction, and the components of the bias magnetic field received by the two magnetic tunnel junctions 2 in the same differential bit along the first direction are opposite, and the components along the initial magnetization direction are the same. Therefore, the initial magnetization along the initial magnetization direction is only needed once, so that the stray field of the bias magnetic field can be opposite to the horizontal component direction of the free layer 21 of the two magnetic tunnel junctions 2 to finish initialization, and the problem of reliable writing and high-speed reading of the perpendicular magnetization MTJ zero magnetic field can be solved at the same time.
The specific structure of a magnetic memory cell provided by the present invention will be described in detail in the following embodiments of the invention.
Referring to fig. 2 to 4, fig. 2 is a schematic structural diagram of a first specific magnetic memory cell according to an embodiment of the present invention, fig. 3 is a schematic structural diagram of a top view of fig. 2, and fig. 4 is a schematic structural diagram of a second specific magnetic memory cell according to an embodiment of the present invention.
The embodiment of the present invention is different from the embodiment of the present invention described above in that the structure of the auxiliary magnetic structure 3 is further defined on the basis of the embodiment of the present invention described above. The rest of the content is described in detail in the above embodiment of the present invention, and will not be described in detail herein.
Referring to fig. 2 and 3, in the embodiment of the present invention, a separation layer 24 is disposed on a surface of the magnetic tunnel junction 2 facing away from the spin-orbit torque providing line 1, the auxiliary magnetic structure 3 includes an auxiliary magnetic layer 31 having an in-plane easy axis and disposed on a surface of the separation layer 24 facing away from the spin-orbit torque providing line 1, magnetic moments of the auxiliary magnetic layer 31 and the first direction have an included angle, so that component directions of magnetic moments of two auxiliary magnetic layers 31 corresponding to a same differential bit along the first direction are opposite, component directions along a second direction are the same, and the second direction is a direction perpendicular to the first direction in a horizontal plane.
In this embodiment, specifically, a corresponding auxiliary magnetic layer 31 is disposed on top of each magnetic tunnel junction 2 facing away from the spin-orbit torque providing line 1, and the auxiliary magnetic layer 31 is configured to provide a bias magnetic field to the corresponding magnetic tunnel junction 2. A separation layer 24 is provided between the auxiliary magnetic layer 31 and the magnetic tunnel junction 2, and the separation layer 24 needs to be made of a conductive material to ensure electrical connection between the auxiliary magnetic layer 31 and the magnetic tunnel junction 2, and to avoid magnetic coupling between the auxiliary magnetic layer 31 and the magnetic tunnel junction 2. The specific material of the separation layer 24 may be set according to the actual situation, and is not particularly limited as long as the above-described functions can be achieved.
In this embodiment, an auxiliary magnetic layer 31 needs to be disposed on top of each magnetic tunnel junction 2, the auxiliary magnetic layer 31 having a magnetic moment in the horizontal direction, and the auxiliary magnetic layer 31 having an in-plane easy axis. In this embodiment, the direction perpendicular to the first direction on the horizontal surface is the second direction, and for each of the auxiliary magnetic layers 31, the magnetic moment of the auxiliary magnetic layer 31 has an angle with the first direction, and the angle makes the magnetic moment of the auxiliary magnetic layer 31 have a component corresponding to the first direction and a component corresponding to the second direction. In this embodiment, two auxiliary magnetic layers 31 are required for one differential bit, and the directions of the components of the two auxiliary magnetic layers 31 corresponding to the first direction are opposite, i.e. the magnetic moment direction of one auxiliary magnetic layer 31 is leftward and the magnetic moment direction of the other auxiliary magnetic layer 31 is rightward along the first direction. The magnetic moments of the two auxiliary magnetic layers 31 are required to be the same in the component direction corresponding to the second direction, and the second direction is the initial magnetization direction, and after the initial magnetization is performed along the second direction, the two auxiliary magnetic layers 31 in the same differential bit can provide magnetic moments in opposite directions along the first direction, so that the directions of stray fields received by the free layers 21 in the two magnetic tunnel junctions 2 in the same differential bit are opposite. When a current is passed in the spin-orbit torque supply line 1, the two free layers 21 will be written in opposite directions, thereby realizing the storage of differential information.
In this embodiment, the auxiliary magnetic layer 31 is made of ferromagnetic material, such as Co, fe, coFe or NiFe, and the auxiliary magnetic layer 31 may be elliptical or rectangular to have the magnetic moment in the above direction. Specifically, in this embodiment, the included angles corresponding to the two auxiliary magnetic layers 31 corresponding to the same differential bit may be complementary angles, that is, the included angle between the magnetic moment of one auxiliary magnetic layer 31 and the first direction in the same differential bit is 45 °, and then the included angle between the magnetic moment of the other auxiliary magnetic layer 31 and the first direction is 135 °, and after initial magnetization, the two auxiliary magnetic layers 31 corresponding to the same differential bit may provide magnetic moment components with equal magnitudes and opposite directions along the first direction. Thus, the directions of the stray fields generated by the auxiliary magnetic layer 31 received by the two free layers 21 of the same differential bit are opposite and equal. When a current is passed in the spin-orbit torque supply line 1, the two free layers 21 will be written in opposite directions.
In the embodiment of the present invention, the value of the included angle between one of the auxiliary magnetic layers 31 corresponding to the same differential bit and the first direction is 20 ° to 70 °, including the end point value, and the value of the included angle between the other auxiliary magnetic layer 31 and the first direction is 110 ° to 160 °, including the end point value. When the included angle is within the above range, the initialization of the differential bit can be completed by applying only one magnetic field.
Referring to fig. 4, further, in this embodiment, the auxiliary magnetic structure 3 may further include a pinning layer 32 located on a side surface of the auxiliary magnetic layer 31 facing away from the spin orbit torque providing line 1, wherein a magnetic moment direction of the pinning layer 32 corresponds to a magnetic moment direction of the contacted auxiliary magnetic layer 31.
That is, in this embodiment, each of the auxiliary magnetic layers 31 is in coupling contact with a corresponding pinned layer 32, and the pinned layers 32 are typically disposed on a side surface of the auxiliary magnetic layer 31 facing away from the spin-orbit torque providing line 1, and each of the auxiliary magnetic layers 31 is typically required to be in coupling contact with a corresponding pinned layer 32, where a differential bit is typically provided with two pinned layers 32. The pinning layer 32 in this embodiment provides exchange bias for the corresponding auxiliary magnetic layer 31, and the pinning layer 32 is typically made of an antiferromagnetic material such as IrMn, ptMn, etc.
At initialization, it is necessary to apply an external magnetic field in the second direction above the Neel temperature (Neel temperature) of the pinned layer 32 and hold it for a while, and to remove the external magnetic field after cooling down, and antiferromagnetic coupling of the pinned layer 32 and the corresponding auxiliary magnetic layer 31 is established. The orientation of the auxiliary magnetic layer 31 is equal in magnitude and opposite in direction along the first direction after initialization, and is not easily disturbed by the external magnetic field due to the effect of the pinning layer 32.
According to the magnetic storage unit provided by the embodiment of the invention, the auxiliary magnetic structure 3 is specifically positioned at the top of the corresponding magnetic tunnel junction 2, so that the stray field of the bias magnetic field can be opposite to the horizontal component direction of the free layers 21 of the two magnetic tunnel junctions 2 only by one-time initial magnetization along the second direction, the initialization is completed, and the reading and writing speed is further increased.
The specific structure of a magnetic memory cell provided by the present invention will be described in detail in the following embodiments of the invention.
Referring to fig. 5 to fig. 7, fig. 5 is a schematic structural diagram of a third specific magnetic memory cell according to an embodiment of the invention, fig. 6 is a schematic structural diagram of a fourth specific magnetic memory cell according to an embodiment of the invention, and fig. 7 is a schematic side view of fig. 6.
The embodiment of the present invention is different from the embodiment of the present invention described above in that the structure of the auxiliary magnetic structure 3 is further defined on the basis of the embodiment of the present invention described above. The rest of the content is described in detail in the above embodiment of the present invention, and will not be described in detail herein.
In the embodiment of the present invention, the auxiliary magnetic structure 3 includes an auxiliary magnetic body 33, and one auxiliary magnetic body 33 provides the bias magnetic field to two magnetic tunnel junctions 2 in the same differential bit. I.e. in this embodiment the auxiliary magnetic structure 3 is in particular a monolithic auxiliary magnetic body 33, instead of a separate component arranged on top of the magnetic tunnel junction 2 as in the previous embodiment. In this embodiment, the bias magnetic field is provided to two magnetic tunnel junctions 2 in one differential bit simultaneously by one auxiliary magnetic body 33. In the present embodiment, two modes are specifically provided, and the above-described functions are realized by one auxiliary magnetic body 33.
Referring to fig. 5, in the embodiment of the present invention, the auxiliary magnetic body 33 is located on the side of the spin orbit torque supply line 1 facing away from the magnetic tunnel junction 2, and the auxiliary magnetic body 33 has perpendicular magnetic anisotropy. In this embodiment a third direction in the vertical plane is determined, which is perpendicular to the spin-orbit-torque providing line 1, i.e. perpendicular to the first direction described above. In this structure, the auxiliary magnetic body 33 is located on the side of the spin orbit torque providing line 1 facing away from the magnetic tunnel junction 2, and the auxiliary magnetic body 33 is required to have perpendicular magnetic anisotropy, which is required to have a high coercive force, and a typical value thereof is required to be generally greater than 2kOe. The auxiliary magnetic body 33 needs to be magnetized in the perpendicular direction, i.e. in the above-mentioned third direction, in which case the auxiliary magnetic body 33 can apply magnetic moments opposite in the first direction to the two magnetic tunnel junctions 2 in the same differential bit.
The auxiliary magnetic body 33 may be rectangular or cylindrical in shape, and the material thereof may be CoPt, coTb, coGa, or the like. This allows the free layers 21 of the two magnetic tunnel junctions 2 in the same differential bit to experience horizontal magnetic fields in opposite directions, thus allowing the differential bit function described above to be implemented, i.e., a single current writes the two magnetic tunnel junctions 2 in opposite states. In addition, by appropriate material optimization, the SAF (antiferromagnetic) stray field inside the magnetic tunnel junction 2 and the vertical (third direction) component of the auxiliary magnetic body 33 to the stray field of the free layer 21 can be canceled, thereby avoiding the influence of the auxiliary magnetic body 33 to the magnetic tunnel junction 2 in the third direction.
In general, the auxiliary magnetic body 33 is located at the middle position of the two magnetic tunnel junctions 2 of the same differential bit, so that the free layers 21 of the two magnetic tunnel junctions 2 in the same differential bit can sense horizontal magnetic fields with equal magnitudes and opposite directions. Of course, the auxiliary magnetic body 33 may be provided not on the side of the spin-orbit torque supply line 1 facing away from the magnetic tunnel junction 2 but on the parallel side of the magnetic tunnel junction 2, or on the side of the magnetic tunnel junction 2 facing away from the spin-orbit torque supply line 1, as long as the above-described function can be achieved. Of course, depending on the location of the magnetic tunnel junction 2, its initial magnetization direction needs to be determined separately. When the auxiliary magnetic body 33 is located on the side of the spin-orbit torque providing line 1 facing away from the magnetic tunnel junction 2 and the auxiliary magnetic body 33 has perpendicular magnetic anisotropy, its distance from the free layer 21 is close, the orientation of the free layer 21 can be sufficiently affected, and at the same time, by appropriate material optimization, the influence of the auxiliary magnetic body 33 on the magnetic tunnel junction 2 in the third direction can be avoided.
Referring to fig. 6 and 7, in the embodiment of the present invention, the magnetic tunnel junction device includes two sets of differential bits, the spin orbit moment providing lines 1 of the two sets of differential bits are parallel, the auxiliary magnetic body 33 is located between the two sets of differential bits, and one auxiliary magnetic body 33 provides the bias magnetic field to the two sets of differential bits, and four magnetic tunnel junctions 2 are provided.
I.e. in this embodiment two sets of differential bits are first provided and the two sets of differential bits are parallel to each other, i.e. the spin-orbit-moment providing lines 1 of the two sets of differential bits are parallel. The auxiliary magnetic body 33 is provided between the two sets of differential bits, and the auxiliary magnetic body 33 can provide the bias magnetic field to the four magnetic tunnel junctions 2 in total.
The two sets of differential bits typically need to be arranged opposite each other, and the auxiliary magnetic body 33 needs to be located between the two sets of differential bits. Specifically, the auxiliary magnetic member 33 may be provided on the side of the spin-orbit torque supply line 1 facing away from the magnetic tunnel junction 2, may be provided in a position parallel to the magnetic tunnel junction 2, or may be provided on the side of the magnetic tunnel junction 2 facing away from the spin-orbit torque supply line 1, as long as the above-described function can be achieved. The auxiliary magnetic body 33 is usually provided on the side of the spin-orbit torque supply line 1 facing away from the magnetic tunnel junction 2, at a position closer to the free layer 21.
In this structure, the shape of the auxiliary magnetic body 33 may be elliptical or rectangular, and the stray field generated by the auxiliary magnetic body may affect two groups of differential bits simultaneously. The initial magnetization direction corresponding to this structure is the second direction, perpendicular to the first direction in which the write current passes. The component of the stray field of the auxiliary magnetic body 33 in the third direction (perpendicular to both the first and second directions) in this structure has less influence on the offset (offset) of the free layer 21 in the magnetic tunnel junction 2.
Typically, the auxiliary magnetic body 33 needs to be located in the middle of two magnetic tunnel junctions 2 of the same differential bit to provide equal and opposite stray fields in the first direction.
It should be noted that, in the application, the top of the magnetic memory cell provided in each embodiment, i.e., the side facing away from the spin-orbit torque providing line 1, is typically provided with a top electrode for electrical connection with other structures.
The auxiliary magnetic structure 3 of the magnetic memory unit provided by the embodiment of the invention is specifically an auxiliary magnetic body 33 which is arranged independently, so that the stray field of the bias magnetic field can be opposite to the horizontal component direction of the free layers 21 of the two magnetic tunnel junctions 2 only by one initial magnetization along the initial magnetization direction, the initialization is completed, and the reading and writing speed is further increased.
The application also provides an SOT-MRAM memory provided with the magnetic memory cell disclosed in any one of the above embodiments. Typically, the SOT-MRAM memory in this embodiment will include a plurality of the magnetic memory cells described above distributed in an array. Other structures related to the SOT-MRAM memory can refer to the prior art, and will not be described herein.
The magnetic memory unit provided by the embodiment of the application can realize the writing of the differential signals only through one initial magnetization, so that the magnetic memory unit has a faster reading and writing speed. The SOT-MRAM provided by the present embodiment can generally have a faster read/write speed, and the initialization process is simpler. The specific structure of a magnetic memory cell provided by the present application is described in detail in the above embodiments of the present application, and will not be described herein.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The magnetic memory cell and SOT-MRAM provided by the present invention are described in detail above. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Claims (10)
1. A magnetic memory cell comprising at least one set of differential bits and an auxiliary magnetic structure, the differential bits comprising:
Spin orbit torque providing lines;
The differential bit has a first direction parallel to the spin-orbit-torque-providing line axis and an initial magnetization direction perpendicular to the first direction;
the auxiliary magnetic structure provides bias magnetic fields for two magnetic tunnel junctions in the same differential bit, the bias magnetic fields have components along the first direction and components along the initial magnetization direction, the component directions of the two bias magnetic fields along the initial magnetization direction are the same, and the component directions of the two bias magnetic fields along the first direction are opposite.
2. The magnetic memory cell of claim 1 wherein a side surface of the magnetic tunnel junction facing away from the spin-orbit torque providing line is provided with a separation layer;
The auxiliary magnetic structure comprises an auxiliary magnetic layer which is positioned on the surface of one side of the separation layer, which is opposite to the spin orbit torque providing line, and is provided with an in-plane easy axis, wherein magnetic moments of the auxiliary magnetic layer and the first direction form an included angle, so that component directions of magnetic moments of two auxiliary magnetic layers corresponding to the same differential bit along the first direction are opposite, component directions along a second direction are the same, and the second direction is a direction perpendicular to the first direction in a horizontal plane.
3. The magnetic memory cell of claim 2 wherein the included angles of the two auxiliary magnetic layers corresponding to the same differential bit are complementary to each other.
4. The magnetic memory cell of claim 3 wherein the angle between one of the auxiliary magnetic layers and the first direction for the same differential bit is in the range of 20 ° to 70 °, inclusive, and the angle between the other auxiliary magnetic layer and the first direction is in the range of 110 ° to 160 °, inclusive.
5. The magnetic memory cell of claim 2 wherein the auxiliary magnetic structure further comprises a pinning layer on a side surface of the auxiliary magnetic layer facing away from the spin-orbit torque providing line, a magnetic moment direction of the pinning layer corresponding to a magnetic moment direction of the auxiliary magnetic layer in contact.
6. The magnetic memory cell of claim 1 wherein the auxiliary magnetic structure comprises an auxiliary magnetic body, one of the auxiliary magnetic bodies providing the bias magnetic field to two of the magnetic tunnel junctions in the same differential bit cell.
7. The magnetic memory cell of claim 6 wherein the auxiliary magnetic body is located on a side of the spin-orbit torque providing line facing away from the magnetic tunnel junction, the auxiliary magnetic body having perpendicular magnetic anisotropy.
8. The magnetic memory cell of claim 6 wherein the auxiliary magnetic body is located in an intermediate position of two of the magnetic tunnel junctions of the same differential bit.
9. The magnetic memory cell of claim 6 including two sets of said differential bits, said spin-orbit moments of two sets of said differential bits providing line parallelism, said auxiliary magnetic body being located between two sets of said differential bits, one said auxiliary magnetic body providing said bias magnetic field to two sets of said differential bits for a total of four said magnetic tunnel junctions.
10. A SOT-MRAM memory, characterized in that it comprises a magnetic memory cell according to any one of claims 1-9.
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