WTe2 Spin-Orbit Torque Switching for Field-Free PMA Magnets
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Spin-Orbit Torque (SOT) devices require an external magnetic field to deterministically switch the magnetization state of perpendicularly magnetic anisotropy (PMA) magnets, limiting their compactness and thermal stability in memory applications.
Innovation Solution
The use of a bilayer system with tungsten ditelluride (WTe2) as a spin-source material, exploiting its low symmetry crystal structure to generate out-of-plane antidamping torque, allowing for field-free deterministic switching of PMA magnets by applying a charge current along specific axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external magnetic field is applied to enable deterministic switching of PMA magnet, then the magnetization state can be switched deterministically, but the device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the external magnetic field component from the system by using WTe2's intrinsic low-symmetry crystal structure to generate the necessary out-of-plane antidamping torque internally through spin galvanic effects, thereby achieving field-free deterministic switching
Solution Approach 2:
The WTe2 material serves itself by utilizing its own low-symmetry crystal structure properties to generate the required torque for magnetization switching without needing external assistance, making the system self-sufficient and eliminating external biasing requirements
2Device complexity
If conventional HM/FM bilayer structure is used, then the device structure is simple, but external magnetic field is required for PMA magnet switching
Solution Approach 1:
The patent changes the material parameter of the spin-source layer from conventional heavy metals to WTe2, which possesses low-symmetry crystal structure with distinct a-axis and b-axis, enabling different spin torque components (out-of-plane antidamping torque along a-axis, in-plane antidamping torque along b-axis) and eliminating the need for external magnetic fields
3Device complexity
If in-plane antidamping torque is used for magnetization switching, then the switching mechanism is simple, but only in-plane magnetization can be switched
Solution Approach 1:
The patent exploits the asymmetric low-symmetry crystal structure of WTe2, where the distinct a-axis and b-axis create asymmetric spin torque components: out-of-plane antidamping torque along the a-axis enables PMA magnet switching, while in-plane antidamping torque along the b-axis enables in-plane magnetization switching, providing versatile magnetization control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables ultra-compact, thermally stable, and energy-efficient deterministic switching of PMA magnets without the need for external magnetic fields, enhancing the potential for advanced magnetic memory technologies.
Implementation Method 1
a charge current density flowing in the plane (x-direction) of a bilayer structure consisting of spin-source material and a FM material results in a spin current flowing in the out-of-plane direction (z direction) via spin galvanic effects
Implementation Method 2
Spin-Orbit Torque (SOT) is an efficient means of manipulating the magnetic state of ferromagnetic (FM) materials
Data Source
AI summary
Disclosed herein are devices and method for realizing field-free deterministic switching of a perpendicularly polarized magnet using SOTs in a quantum material with low-symmetry crystal structure. In preferred embodiments, SOT devices are fabricated using a perpendicularly polarized van der Waals (vdW) based layered quantum material platform and thin films of WTe2 are used as a spin-source material for generating the SOTs for magnetic memory and spin logic devices.