阅读说明：本技术 基于自旋轨道转矩无磁场翻转的钴铂钌钴铂磁存储器件 (Spin orbit torque-based magnetic field-free overturning cobalt-platinum-ruthenium-cobalt magnetic memory device ) 是由 樊浩东 冯重舒 庄燕山 周铁军 李文钧 骆泳铭 于 2021-06-21 设计创作，主要内容包括：本发明公开了一种基于自旋轨道转矩无磁场翻转的钴铂钌钴铂磁存储器件。结构从下到上依次为：衬底层、缓冲层、导电层、薄膜层、保护层；所述的薄膜层由CoPtRuCoPt五层构成。当所述导电层Pt将通入的电荷流转换为自旋流,通过Pt的强自旋轨道耦合将自旋流注入到铁磁层中,从而对铁磁层施加转矩。改变直角梯形Ru的厚度,可打破空间反演对称性,并调控双层钴铂之间的层间交换耦合,从而实现无磁场的磁化翻转。当接入脉冲电流且没有面内辅助磁场时,每增加一次脉冲电流的大小,就记录一次霍尔电阻的值,当霍尔电阻的值随着脉冲电流增大而跳变进而形成回路时,即可理解为磁存储状态的切换,进而实现无磁场的磁存储操作。(The invention discloses a spin orbit torque magnetic field-free overturning-based cobalt-platinum-ruthenium-cobalt-platinum magnetic memory device. The structure from bottom to top is as follows: the substrate layer, the buffer layer, the conducting layer, the thin film layer and the protective layer; the thin film layer is composed of five layers of CoPtRuCoPt. When the conductive layer Pt converts an introduced charge current into a spin current, the spin current is injected into the ferromagnetic layer by strong spin-orbit coupling of Pt, thereby applying a torque to the ferromagnetic layer. The thickness of the right-angle trapezoid Ru is changed, the symmetry of space inversion can be broken, and interlayer exchange coupling between double layers of cobalt and platinum is regulated and controlled, so that magnetization overturning without a magnetic field is realized. When the pulse current is switched in and the in-plane auxiliary magnetic field does not exist, the value of the Hall resistor is recorded once when the pulse current is increased once, and when the value of the Hall resistor jumps along with the increase of the pulse current to form a loop, the switching of the magnetic storage state can be understood, so that the magnetic storage operation without the magnetic field is realized.)

1. The cobalt platinum ruthenium cobalt platinum magnetic memory device based on spin orbit torque non-magnetic field upset is characterized in that the magnetic memory device has a multilayer film structure, and the structure sequentially comprises from bottom to top: the substrate layer, the buffer layer, the conducting layer, the thin film layer and the protective layer; the thin film layer structure sequentially comprises a Co layer, a Pt layer, a Ru layer, a Co layer and a Pt layer from bottom to top; the thickness of the two layers of Co is 0.8nm, the thickness of the two layers of Pt is 0.2nm, the thickness of the Ru layer is of a right-angle trapezoidal structure, and the thickness of the Ru layer is 0.6-1.4 nm; the height difference of two sides of the right-angle trapezoid structure is 0.1-0.2 nm.

2. The cobalt-platinum-ruthenium-cobalt-platinum magnetic memory device based on spin-orbit torque field-free switching as claimed in claim 1, wherein the buffer layer is made of Ta and has a thickness of 1nm, so that the thin film layer can be better adhered to the substrate layer, and the flatness of the thin film can be improved.

3. The spin-orbit torque field-free switching cobalt platinum magnetic memory device according to claim 1, wherein the conductive layer is Pt with a thickness of 5.5nm, and functions to convert an introduced charge current into a spin current, which is injected into Co of the thin film layer through strong spin-orbit coupling of Pt.

4. The cobalt platinum ruthenium cobalt platinum magnetic memory device based on spin orbit torque magnetic field reversal free, according to claim 1, wherein the protective layer is made of Ta with a thickness of 3nm, and the bottom thin film is protected from oxidation, thereby improving the stability of the device.

5. The spin-orbit torque field-free switching cobalt platinum ruthenium cobalt platinum based magnetic memory device of claim 1, wherein: the substrate layer should be Si/SiO₂The Si surface has 500nm SiO₂Covering to isolate the substrate from the film and prevent leakage of current.

6. The spin-orbit torque field-free switching cobalt platinum ruthenium cobalt platinum based magnetic memory device of claim 1, wherein: the magnetic memory device is of a Hall Bar structure.

7. The spin-orbit torque field-free switching cobalt platinum ruthenium cobalt platinum based magnetic memory device of claim 1, wherein: when the conducting layer is used for accessing pulse current and has no in-plane auxiliary magnetic field, the value of the Hall resistor is recorded once when the pulse current is increased once, and when the value of the Hall resistor jumps along with the increase of the pulse current and forms a loop, the switching of a magnetic storage state can be understood, so that the magnetic storage operation without the magnetic field is realized.

Technical Field

The invention belongs to the field of magnetic storage, and particularly relates to a spin orbit torque-based magnetic field-free overturning cobalt-platinum magnetic storage device.

Technical Field

Due to the potential application of Perpendicular Magnetic Anisotropy (PMA) ferromagnets in low power consumption, non-volatile memory and logic devices, switching their magnetization by spin-orbit torque (SOT) has been one of the hot spots of research in the field of current magnetic storage. A typical SOT device consists of a heavy metal/ferromagnetic/heavy metal structure in which, when an in-plane charge current flows in a heavy metal layer, a spin-only current is generated by the spin hall effect or the interfacial Rashba effect and injected into and applies an SOT to the ferromagnetic layer, pulling its magnetic moment to flip. By adjusting the film thickness, the double-layer cobalt platinum (CoPtCoPt) film has stronger PMA, and can realize magnetization reversal assisted by a magnetic field at present. However, an in-plane external magnetic field is usually required to assist the perpendicular magnetization switching, which is a significant obstacle to practical applications. In order to achieve field-free SOT switching, thin film structures with additional torque in themselves must be designed, and several designs that introduce an effective in-plane field have been experimentally demonstrated: introducing a wedge-shaped structure; coupling with another ferromagnetic layer by in-plane anisotropy; exchange bias with the in-plane antiferromagnetic layer, etc.

Magnetic memory devices based on spin-orbit torque without magnetic field switching have advantages over conventional memory devices in higher storage density, better thermal stability and lower power consumption. In addition, an in-plane auxiliary magnetic field is not needed, and only the magnetization of the magnetic field is controlled to be inverted by current, so that the magnetic field has great significance to low-power consumption, nonvolatile memories and logic devices.

Disclosure of Invention

The invention belongs to the field of magnetic storage, and particularly relates to a spin orbit torque-based magnetic field-free overturning cobalt-platinum magnetic storage device.

The magnetic storage device is a cobalt platinum ruthenium cobalt platinum magnetic storage device based on spin orbit torque without magnetic field inversion, and has a multilayer film structure, and the structure sequentially comprises the following components from bottom to top: the substrate layer, the buffer layer, the conducting layer, the thin film layer and the protective layer; the thin film layer structure sequentially comprises a Co layer, a Pt layer, a Ru layer, a Co layer and a Pt layer from bottom to top; the thickness of the two layers of Co is 0.8nm, the thickness of the two layers of Pt is 0.2nm, the thickness of the Ru layer is of a right-angle trapezoidal structure, and the thickness of the Ru layer is 0.6-1.4 nm; the height difference of two sides of the right-angle trapezoid structure is 0.1-0.2 nm.

Preferably, the buffer layer is made of Ta, and the thickness of the buffer layer is 1nm, so that the thin film layer and the substrate layer are better adhered, and the flatness of the thin film is improved.

Preferably, the conductive layer should be Pt with a thickness of 5.5nm, which functions to convert an introduced charge current into a spin current, which is injected into Co of the thin film layer by strong spin-orbit coupling of Pt.

Preferably, the protective layer is made of Ta, the thickness of the protective layer is 3nm, and the bottom film is protected from being oxidized, so that the stability of the device is improved.

Preferably, the substrate layer should be Si/SiO₂The Si surface has 500nm SiO₂Covering to isolate the substrate from the film and prevent leakage of current.

Preferably, the magnetic memory device is of a Hall Bar structure.

Preferably, when the conductive layer is used for connecting a pulse current and has no in-plane auxiliary magnetic field, the value of the hall resistor is recorded once every time the pulse current is increased, and when the value of the hall resistor jumps along with the increase of the pulse current and forms a loop, the switching of the magnetic storage state can be understood, so that the magnetic storage operation without the magnetic field is realized.

The preparation method of the spin orbit torque magnetic field reversal-free cobalt-platinum magnetic memory device comprises the following steps: firstly, Si/SiO₂Carrying out magnetron sputtering on a Ta/Pt/Co/Pt/Ru/Co/Pt/Ta layer on a substrate; then, preparing Hall Bar through a micro-nano processing technology of photoetching, etching and alignment; finally, a platinum electrode with the thickness of 50nm is formed by magnetron sputtering. The device is then tested for magnetization switching.

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

1. magnetic memory devices based on spin-orbit torque without magnetic field switching have advantages over conventional memory devices in higher storage density, better thermal stability and lower power consumption.

2. Compared with the traditional magnetic storage device, the magnetic storage device is provided with the advanced thin film layer, so that the magnetization reversal of the magnetic storage device can be realized only by current control without an in-plane auxiliary magnetic field, and the magnetic storage device has great significance for low-power-consumption nonvolatile memories and logic devices.

Drawings

FIG. 1 is a schematic diagram of an SOT-based magnetic memory structure;

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

FIG. 3Hall Bar structural diagram;

FIG. 4 is a hysteresis loop diagram of the device under test;

FIG. 5 is a field-free magnetization reversal diagram of the device under test.

Detailed Description

The invention aims to provide a spin orbit torque-based magnetic field reversal-free cobalt-platinum magnetic memory. The invention utilizes the principle of spin orbit torque to convert the introduced charge flow into spin flow, and injects the spin flow into the ferromagnetic layer through the strong spin orbit coupling of Pt, thereby applying torque to the ferromagnetic layer. An advanced multilayer thin film structure is designed, interlayer exchange coupling between double layers of cobalt and platinum is regulated and controlled through direct trapezoidal Ru, and magnetization overturning without a magnetic field is achieved.

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

cobalt-platinum-ruthenium-cobalt-platinum magnetic memory based on spin orbit torque and without magnetic field overturning

1) Alternating current is introduced into the X direction of the device, control voltage is introduced out of the surface of the device, the direction of the magnetic field to be measured is consistent with the X direction of the device, voltage can be collected at the two electrodes in the Y direction, and a hysteresis loop of the corresponding device can be obtained.

2) The method comprises the steps of introducing pulse current with continuously increased amplitude to the X direction of a device, recording the value of a Hall resistor once when the pulse current is increased once, and when the value of the Hall resistor jumps along with the increase of the pulse current to form a loop, understanding the switching of a magnetic storage state, so that the magnetic storage operation without a magnetic field is realized.

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

as shown in fig. 1, the SOT-based magnetic random access memory adopts a three-terminal read/write method: two write terminals and one read terminal. The reading path and the writing path are mutually independent and mutually perpendicular, do not interfere with each other, can respectively optimize the writing path and the reading path, and realize smaller, faster, more efficient and more stable storage.

As shown in fig. 2, the buffer layer is made of buffer material Ta, and the thickness of the buffer layer is 1nm, so that the thin film layer and the substrate layer are better adhered to each other, and the flatness of the thin film is improved. The conductive layer should be conductive material Pt with a thickness of 5.5 nm. The effect is to convert the introduced charge flow into spin flow, and the spin flow is injected into the ferromagnetic layer through the strong spin-orbit coupling of Pt, thereby applying a torque to the ferromagnetic layer. The thin film layer is composed of five layers of CoPtRuCoPt, the thickness of Co is 0.8nm, the thickness of Pt is 0.2nm, the thickness of Ru layer is of a right-angle trapezoidal structure, the thickness of Ru layer is 0.6-1.4nm, and the height difference of two sides of the right-angle trapezoidal structure is 0.1-0.2 nm. The double-layer Co-Pt (0.8) Pt (0.2) Co (0.8) Pt (0.2) film has stronger PMA, a layer of right-angle trapezoid Ru is added between the double-layer Co-Pt (0.8) Pt (0.2) film, the thickness of the right-angle trapezoid Ru is changed, interlayer exchange coupling between the double-layer Co-Pt film and the double-layer Pt film can be adjusted, and the symmetry of space inversion is broken, so that the magnetization reversal without a magnetic field is realized. The protective layer is made of Ta, the thickness of the protective layer is 3nm, the thin film at the bottom is protected from being oxidized, and the stability of the device is improved.

As shown in FIG. 3, the Hall Bar structure is a central cross part, and the length of the current terminal (X) and the length of the voltage terminal (Y) are both 10 multiplied by 100 μm. There are also four electrode areas for wire bonding to the test port. The grown thin film is only left on the middle cross part through the photoetching process, and the structure design is favorable for magnetization turning.

As shown in fig. 4, the hysteresis loop of the device CoPtRuCoPt. When a magnetic field in the out-of-plane direction is applied, the applied magnetic field is increased from-3500 (Oe) to 3500(Oe) and then decreased from 350o (Oe) to-3500 (Oe). It can be clearly observed that the sample has a very strong perpendicular magnetic anisotropy, indicating that the device is suitable as a candidate for a magnetic memory.

As shown in fig. 5, when a pulse current with an increasing amplitude is applied to the device X, hall resistance signals are collected at two ends of the voltage current. It can be observed that when the magnitude of the pulse current is applied to 35mA, the hall resistance changes drastically and the magnetic memory state transitions between spin-up and spin-down. In addition, the magnetization switching is completed without the assistance of an external in-plane field, namely, without magnetic field switching. It can be speculated that the magnetic field-free overturning is realized by regulating and controlling interlayer exchange coupling between double layers of cobalt and platinum through Ru and breaking space inversion symmetry.