Spin-orbit-torque element with antiferromagnetic layer
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Solution Overview
Problem
Existing spin-orbit-torque magnetoresistance effect elements face challenges in achieving fast magnetization rotation due to inefficiencies in spin current generation and stability issues caused by ferromagnetic substances used in wiring, leading to reduced MR ratio and magnetization stability, which can result in unexpected data rewriting.
Innovation Solution
A spin-orbit-torque magnetization rotational element is designed with an antiferromagnetic layer and a first ferromagnetic layer magnetically coupled by exchange coupling, where the antiferromagnetic layer is shorter than the spin-orbit-torque wiring, and a nonmagnetic metal with d and f electrons is used to generate a pure spin current, enhancing magnetization rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ferromagnetic substance and antiferromagnetic substance are used as wiring to generate spin current, then magnetization reversal can be achieved, but the spin current generation efficiency is low and magnetization stability is reduced
Solution Approach 1:
The patent extracts the ferromagnetic substance from the wiring structure and places it only in the form of a thin film layer. The wiring is changed to a nonmagnetic heavy metal material that does not generate parasitic magnetic fields, thereby eliminating the source of magnetization instability while preserving the spin current generation capability through the spin Hall effect.
Solution Approach 2:
The patent employs a composite structure consisting of a nonmagnetic heavy metal wiring layer, an antiferromagnetic thin film layer, and a ferromagnetic thin film layer. This composite material structure leverages the spin Hall effect of the heavy metal, the exchange bias of the antiferromagnetic layer, and the magnetization properties of the ferromagnetic layer to achieve efficient and stable magnetization reversal.
2Power
If ferromagnetic substance is used in wiring, then spin current can be generated, but magnetic field interference reduces MR ratio
Solution Approach 1:
The patent removes the ferromagnetic substance from the wiring function and assigns it only to the thin film layer where it is needed for magnetization reversal. The wiring is replaced with nonmagnetic heavy metal material, eliminating the parasitic magnetic field that interferes with the MR ratio while maintaining spin current generation through the spin Hall effect.
Solution Approach 2:
The patent introduces an antiferromagnetic thin film layer as an intermediary between the nonmagnetic heavy metal wiring and the ferromagnetic thin film layer. This intermediary layer mediates the spin current transfer and provides exchange bias to stabilize the magnetization direction, thereby protecting the MR ratio from degradation while enabling efficient spin current generation.
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
The solution enables faster magnetization rotation and improved stability of the free layer, reducing the time required for magnetization reversal and minimizing the impact of magnetic fields on the MR ratio, thus enhancing data integrity and storage efficiency.
Implementation Method 1
a mode of performing writing (magnetization reversal) using a spin-orbit torque (SOT) caused by a pure spin current generated by a spin-orbit interaction
Implementation Method 2
A current for inducing an SOT in a magnetoresistance effect element flows in a direction that intersects the lamination direction of the magnetoresistance effect element. That is, there is no need to cause a current to flow in the lamination direction of the magnetoresistance effect element, and thus the lifespan of the magnetoresistance effect element longer is expected to be longer. An SOT is induced by a pure spin current generated by a spin-orbit interaction or the Rashba effect at an interface with a heterogeneous material.
Implementation Method 3
a first ferromagnetic layer located on a side of the antiferromagnetic layer opposite to the spin-orbit-torque wiring and magnetically coupled with the antiferromagnetic layer by exchange coupling
Implementation Method 4
A giant magnetoresistance (GMR) element made up of a multilayered film having a ferromagnetic layer and a nonmagnetic layer
Implementation Method 5
tunneling magnetoresistance (TMR) element using an insulating layer (a tunnel barrier layer, a barrier layer) for a nonmagnetic layer
Data Source
AI summary
A spin-orbit-torque magnetization rotational element includes: a spin-orbit-torque wiring extending in a first direction; an antiferromagnetic layer laminated on one surface of the spin-orbit-torque wiring; and a first ferromagnetic layer located on a side of the antiferromagnetic layer opposite to the spin-orbit-torque wiring and magnetically coupled with the antiferromagnetic layer by exchange coupling, wherein a length of the antiferromagnetic layer in the first direction is shorter than a length of the spin-orbit-torque wiring in the first direction.