Spin-Orbit Torque Magnetization Rotation for Low Current Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetization rotation in TMR and GMR elements requires high reversal current density, which is energetically inefficient and can lead to reduced lifespan, and existing methods for reducing current density, such as using spin transfer torque, do not effectively address the issue of element size and longevity.
Innovation Solution
A spin current magnetization rotational element is developed, utilizing a magnetoresistive effect element with a first ferromagnetic metal layer, a second ferromagnetic metal layer, and a non-magnetic layer, along with spin-orbit torque wiring that intersects the stacking direction, allowing for pure spin current generation and reduced electric current flow, thereby lowering current density and increasing element lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spin transfer torque (STT) is used to perform magnetization rotation by passing current through the stacking direction of the magnetoresistive element, then writing efficiency improves and current requirement decreases with element size, but the reversal current density becomes excessively high
Solution Approach 1:
The patent segments the current path into two separate paths: one for writing (through the spin-orbit torque wiring adjacent to the ferromagnetic layer) and one for reading (through the magnetoresistive element stacking direction). This segmentation allows the writing current to flow through a dedicated spin-orbit torque wiring rather than through the magnetoresistive element, thereby reducing the reversal current density and extending element lifespan while maintaining writing efficiency
Solution Approach 2:
The patent introduces a spin-orbit torque wiring as an intermediary component that generates spin-orbit torque to rotate the magnetization of the ferromagnetic layer. This intermediary structure enables magnetization rotation without requiring high current density through the magnetoresistive element itself, thus protecting the element from degradation while achieving effective writing
2Device complexity
If magnetic field method is used for writing, then element structure is simpler, but writing becomes impossible when element size is small due to insufficient current flow through fine wires
Solution Approach 1:
The patent replaces the magnetic field method (which relies on current loops generating external magnetic fields) with a spin-orbit torque method where spin-polarized current directly interacts with the ferromagnetic layer's magnetization. This substitution enables effective writing in miniaturized elements where external magnetic field generation becomes impractical, while the element structure remains relatively simple
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 use of pure spin current for magnetization rotation reduces the reversal current density through the magnetoresistive effect element, enhancing energy efficiency and extending its lifespan by utilizing spin-orbit torque generated by pure spin current.
Implementation Method 1
magnetization rotation using pure spin current generated by spin-orbit interaction has been advocated as a practically applicable method
Implementation Method 2
Pure spin current generated by spin-orbit interaction induces spin-orbit torque (SOT), and this SOT can cause magnetization rotation depending on the magnitude of the SOT
Implementation Method 3
Giant magnetoresistive (GMR) elements composed of a multilayer film of ferromagnetic layers and non-magnetic layers
Implementation Method 4
tunnel magnetoresistive (TMR) elements which use insulating layers (tunnel barrier layers, barrier layers) for the non-magnetic layers
Implementation Method 5
one ferromagnetic layer (the fixed layer or reference layer) causes spin polarization of the current, that current spin is transferred to the magnetization of the other ferromagnetic layer (the free layer or recording layer), and the torque (STT) generated at that time is used to perform writing (magnetization rotation)
Data Source
AI summary
This spin current magnetization rotational type magnetoresistive element includes a magnetoresistive effect element having a first ferromagnetic metal layer having a fixed magnetization orientation, a second ferromagnetic metal layer having a variable magnetization orientation, and a non-magnetic layer sandwiched between the first ferromagnetic metal layer and the second ferromagnetic metal layer, and spin-orbit torque wiring which extends in a direction that intersects the stacking direction of the magnetoresistive effect element, and is connected to the second ferromagnetic metal layer, wherein the electric current that flows through the magnetoresistive effect element and the electric current that flows through the spin-orbit torque wiring merge or are distributed in the portion where the magnetoresistive effect element and the spin-orbit torque wiring are connected.