Spin-Orbit Torque Magnetoresistive Element with High Spin Conductivity Cap
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Solution Overview
Problem
Magnetoresistance effect elements using spin-orbit torque (SOT) face challenges in efficiently supplying pure spin current due to disturbed laminated interfaces when a bottom pin structure is applied, leading to inefficient magnetization rotation and potential noise generation.
Innovation Solution
A spin current magnetization rotational magnetoresistance effect element is designed with a cap layer having high spin conductivity, a diffusion prevention layer, and a spin-orbit torque wiring extending intersecting the lamination direction, which includes a pure spin current generation part and a low resistance part, to efficiently utilize SOT and prevent spin diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bottom pin structure is applied to magnetoresistance effect element, then the structure flexibility is improved, but the interface uniformity deteriorates leading to inefficient spin current supply
Solution Approach 1:
The patent inverts the conventional bottom pin structure to a top pin structure, where the pinned layer is positioned above the free layer instead of below. This inversion resolves the interface uniformity problem by ensuring that the critical spin current supply path from the cap layer through the free layer to the nonmagnetic layer remains undisturbed, while still maintaining the structural flexibility needed for device design.
Solution Approach 2:
The patent introduces a spin current supply layer (cap layer) made of materials with high spin conductivity (such as Ru, Rh, Ir, Cu, Ag, Au, or their alloys) as an intermediary component. This cap layer is positioned between the upper electrode and the free layer to efficiently mediate and supply spin current to the free layer, compensating for any potential interface issues and enhancing the overall spin current supply efficiency.
2Productivity
If current flows in lamination direction for STT magnetization rotation, then the writing efficiency is improved, but the element lifespan deteriorates
Solution Approach 1:
The patent transitions from the conventional spin transfer torque (STT) method where current flows in the lamination direction to a spin-orbit torque (SOT) method where current flows in a direction intersecting the lamination direction (in-plane direction). By changing the dimension of current flow from vertical (through layers) to horizontal (parallel to layers), the patent achieves efficient magnetization rotation through spin Hall effect while avoiding current-induced damage to the element structure, thus extending element lifespan.
3Area of moving object
If element size is reduced for high integration, then the integration density is improved, but the spin current supply efficiency deteriorates
Solution Approach 1:
The patent applies local quality optimization by using materials with high spin conductivity (such as Ru, Rh, Ir, Cu, Ag, Au or their alloys) specifically for the cap layer and spin current supply path. This localized material selection ensures that spin current is efficiently supplied to the free layer even in miniaturized elements, maintaining high spin current supply efficiency despite reduced element size and enabling high integration density.
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
This configuration allows for efficient utilization of SOT-induced magnetization rotation with reduced noise and prolonged element lifespan by ensuring uniform interfaces and effective spin current supply, even in small-sized elements.
Implementation Method 1
it has been proposed that magnetization rotation utilizing spin-orbit interaction induced by a pure spin current can be used for applications
Implementation Method 2
The magnetoresistance effect element in which the spin-orbit interaction is performed induces a spin-orbit torque (SOT) by a pure spin current and the SOT causes magnetization rotation to occur
Implementation Method 3
the cap layer includes one or more substances having high spin conductivity selected from the group consisting of Cu, Ag, Mg, Al, Si, Ge, and GaAs as a major component
Implementation Method 4
A giant magnetoresistance (GMR) element formed of a multilayer film including a ferromagnetic layer and a nonmagnetic layer
Implementation Method 5
tunnel magnetoresistance (TMR) element in which an insulating layer (a tunnel barrier layer, a barrier layer) is used for a nonmagnetic layer
Data Source
AI summary
A spin current magnetization rotational magnetoresistance effect element includes a magnetoresistance effect element including a first ferromagnetic metal layer in which a direction of magnetization is fixed, a second ferromagnetic metal layer configured for a direction of magnetization to be changed, and a nonmagnetic layer provided between the first ferromagnetic metal layer and the second ferromagnetic metal layer and a spin-orbit torque wiring extending in a first direction intersecting a lamination direction of the magnetoresistance effect element and joined to the second ferromagnetic metal layer. Furthermore, in the spin current magnetization rotational magnetoresistance effect element, the spin-orbit torque wiring containing a pure spin current generation part made of a material that generates a pure spin current and a low resistance part made of a material having electric resistance lower than electrical resistance of the pure spin current generation part.