CN113437210A

CN113437210A - Current regulation and control magnetic random access memory based on spin orbit torque

Info

Publication number: CN113437210A
Application number: CN202110703321.8A
Authority: CN
Inventors: 冯重舒; 周铁军; 骆泳铭; 樊浩东; 庄燕山
Original assignee: Hangzhou Dianzi University
Current assignee: Hangzhou Dianzi University
Priority date: 2021-06-24
Filing date: 2021-06-24
Publication date: 2021-09-24
Anticipated expiration: 2041-06-24
Also published as: CN113437210B

Abstract

The invention discloses a current regulation and control magnetic random access memory based on spin orbit torque. The invention comprises a protective layer, a thin film layer, a conductive layer and a buffer layer from top to bottom, wherein the conductive layer is used for accessing control current, so that the size of the vertical anisotropy of the thin film layer is regulated and controlled, and the resistance of the magnetic random access memory is regulated. The structure formed by etching and micro-nano processing the thin film layer and the buffer layer Is a cross structure, the thin film layer Is composed of Pt, Co, Pt and Co structures from top to bottom, when the regulating current Is led in the direction parallel to the thickness direction of the sensing device Is a fixed value, the constant current I Is led in two transverse electrodes of the sensing device, the change of the resistance value of the thin film layer Is detected, and when the fixed current in the same direction Is led in continuously, the resistance value of the resistance can be changed continuously. The invention can realize high-efficiency storage through current regulation and control.

Description

Current regulation and control magnetic random access memory based on spin orbit torque

Technical Field

The invention belongs to the field of magnetic random access memories, and particularly relates to a magnetic random access memory driven by current based on spin orbit torque.

Technical Field

In the last 80 th century, John Slonczewski and Luc Berger proposed the concept of spin transfer torque: the flow of electrons with spin polarization can transfer angular momentum from one magnet to another, and the excited spin wave can even switch the magnetization direction. Spin currents generated based on strong spin-orbit coupling also affect neighboring magnetic materials in the form of a torque, i.e., spin-orbit torque. When spin orbit torque is applied to the technical field, the most concerned problem is the conversion efficiency between charge current and spin current, and the higher the conversion efficiency means the lower the operating energy consumption of the device. Therefore, physicists are continuously exploring the conversion efficiency between spin current and charge current in different structures of different materials, and hopefully discovering the physical mechanism affecting the conversion efficiency and finding materials with higher conversion efficiency.

Compared with the existing magnetic random access memory, the magnetic random access memory based on the spin orbit torque has the advantages of smaller volume, lower power consumption and smaller noise, and is a magnetic random access memory which is easy to realize by a large-scale preparation process.

Disclosure of Invention

A magnetic random access memory driven by current based on spin orbit torque is structurally characterized in that: the magnetic random access memory comprises a protective layer, a thin film layer, a conductive layer and a buffer layer from top to bottom in sequence, wherein the conductive layer is used for accessing control current so as to regulate and control the size of the vertical anisotropy of the thin film layer and regulate the resistance of the magnetic random access memory; the structure formed by etching and micro-nano processing the protective layer, the thin film layer, the conducting layer and the buffer layer is a cross structure, the thin film layer is composed of Pt, Co, Pt, Co and Pt structures from top to bottom, the thicknesses of the two layers of Pt are 0.2-0.3nm, the thickness of the upper layer of Co is 0.4-0.6nm, the thickness of the lower layer of Co is 1.0-1.2nm or the thickness of the upper layer of Co is 1.0-1.2nm, and the thickness of the lower layer of Co is 0.4-0.6 nm. When the regulating current Is led in the direction perpendicular to the thickness direction of the sensing device, the measuring voltage Us Is led in the two transverse electrodes of the sensing device, the change of the resistance value of the thin film layer Is detected, and when the currents in the same direction and different magnitudes are continuously led in, the resistance can be continuously changed to an extreme value.

Preferably, the protective layer should be a protective material, Ta, with a thickness of 3-5 nm.

Preferably, the conductive layer should be a conductive material, Pt, and 5nm thick.

Preferably, the buffer layer is made of buffer material Ta and has a thickness of 3-5 nm.

The Ta layer is used as a buffer layer and aims to prevent the continuity of the film appearance from being damaged when being heated during the orientation growth. The effect of the four layers of Co/Pt in the thin film layer is to change the vertical anisotropy by changing the thickness of the upper and lower layers. When the upper and lower layers of Co/Pt have different vertical anisotropy, the symmetry is destroyed, so that when current passes through the magnetic domain, the magnetic domain can be slowly deflected according to the direction of spin current without an external magnetic field, and the resistance is changed.

The conductive layer composed of Pt functions to provide the necessary spin current for domain inversion of the Co/Pt bilayer film of the thin film layer.

A method for preparing a current regulation magnetic random access memory based on spin orbit torque comprises the following steps: sputtering a Ta layer, a Pt layer, a Co layer, a Pt layer and a Ta layer on a silicon substrate; and then, etching, carrying out micro-nano processing to form a cross structure, and continuously plating electrodes on the reserved positions on four pins of the cross structure.

Compared with the background art, the invention has the beneficial effects that:

1. compared with the existing magnetic memory, the current regulation and control magnetic random access memory of the spin orbit torque only depends on the current, and the storage density is higher.

2. The spin orbit torque based magnetic random access memory has a small volume, low power consumption, and non-volatility compared to a conventional random access memory device.

Drawings

FIG. 1 is a block diagram of a magnetic memory;

FIG. 2 is a cross-sectional view of a thin film structure;

FIG. 3 is a hysteresis loop plot of the film itself;

FIG. 4 is a cross structure view of the device;

FIG. 5 is a diagram showing the resistance change of the device after a control pulse current is applied;

Detailed Description

The invention aims to provide a magnetic random access memory driven by current based on spin orbit torque. The invention comprises the following steps: the different magnetic moments of the ferromagnetic materials Co with different thicknesses cause the magnetic moments of Co to be more easily shifted to different directions by applying spin current due to the lack of symmetry. Which subsequently causes a change in its resistance.

The purpose of the invention is realized by the following technical scheme:

current-driven magnetic random access memory based on spin orbit torque

1) Pulse current Is led into the two electrodes of the device in the X direction, and voltage Us can be collected at the two electrodes in the Y direction, so that the numerical value of the thin film resistance can be obtained.

2) After pulse currents with different intensities are applied along a fixed direction, the currents can provide self-spin current for the magnetic domain of the thin film layer to turn over, and the resistance of the thin film layer gradually changes along with the continuous turning over of the magnetic domain of the thin film layer. Then, the magnetic domain will gradually return to the initial state after the pulse current in the opposite direction is applied.

The invention is further described below with reference to the accompanying drawings and examples:

as shown in FIG. 1, the devices are a Ta layer, a Pt layer, a Co layer, a Pt layer and a Ta layer from bottom to top. When the direction of the initially introduced pulse current is set to be the positive X direction, the resistance is continuously changed, and the corresponding resistance can be calculated through the collected voltage U in the Y direction.

As shown in FIG. 2, the Ta layer serves as a buffer layer to prevent the continuity of the film topography from being destroyed upon heating during the orientation growth. ② the lowest Pt layer used as a conductive layer can provide spin current for the upper film. ③ the Co/Pt and Co/Pt multilayer films have different thicknesses and different vertical anisotropies. The uppermost Ta has good oxidation resistance to act as a protective layer. Pt serves as a conductive layer.

As shown in fig. 3, is the hysteresis loop of the device. The magnetization performance of the thin film layer is reflected;

as shown in fig. 4, four

regions

1, 2, 3, and 4 are electrode regions, and 5 is a thin film sample region.

As shown in fig. 5, when the intensity of the pulse current is continuously increased in the x direction of the device, the resistance value thereof is slowly changed by the current. Wherein the curve shown by the circular symbol is an overturning curve of the thickness of the Co on the upper layer of the thin film layer being 0.4-0.6nm and the thickness of the Co on the lower layer being 1.0-1.2 nm; the curve shown by the square symbol is an inverted curve in which the thickness of Co on the upper layer of the thin film layer is 1.0-1.2nm and the thickness of Co on the lower layer is 0.4-0.6 nm.

Claims

1. A current regulation and control magnetic random access memory based on spin orbit torque is characterized in that a magnetic field sensing device has a multilayer film structure, and the structure is as follows: the protective layer, the thin film layer, the conducting layer and the buffer layer are sequentially arranged from top to bottom, and the conducting layer is used for accessing regulating current and measuring voltage, so that the resistance of the conducting layer is controlled by continuously applying pulse current; the structure formed by etching and micro-nano processing the protective layer, the thin film layer, the conducting layer and the buffer layer is a cross structure, the thin film layer is composed of Co and Pt multilayer films and is composed of Pt, Co, Pt and Co structures from top to bottom, and the thicknesses of the two layers of Pt are 0.2-0.3 nm; the thickness of the upper layer Co is 0.4-0.6nm, the thickness of the bottom layer Co is 1.0-1.2nm, or the thickness of the bottom layer Co is 0.4-0.6nm, and the thickness of the upper layer Co is 1.0-1.2 nm.

2. The spin-orbit torque-based current steering MRAM according to claim 1, wherein the conductive layer is a conductive material, Pt, and has a thickness of 3-5 nm.

3. The spin-orbit torque-based current steering MRAM of claim 1, wherein the protective layer is a protective material, Ta, and has a thickness of 3-5 nm.

4. The spin-orbit torque-based current steering MRAM of claim 1, wherein the buffer layer is a buffer material Ta and has a thickness of 3-5 nm.

5. The spin orbit torque based current steering mram of claim 1, wherein: pulse current Is led into the two electrodes of the device in the X direction, voltage Us can be collected at the two electrodes in the Y direction, and the resistance of the device changes correspondingly along with the continuous change of the intensity of the pulse current Is, so that information storage Is realized.