Laminated Spin-Orbit Torque Wiring for Low-Current Magnetization Reversal
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Solution Overview
Problem
Current spin-orbit torque wiring materials for magnetoresistance effect elements face challenges in achieving low resistance while effectively producing both spin Hall and interface Rashba effects, leading to high power consumption and difficulties in lattice matching with ferromagnetic metal layers.
Innovation Solution
A spin current magnetization rotational element is designed with a laminated structure of a spin conduction layer and a spin generation layer, where the ratio of their film thicknesses is optimized to match their resistivities, and materials with specific cubic crystal structures are used to enhance the spin Hall effect and interface Rashba effect, reducing power consumption and lattice mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If heavy metal materials such as Ta are used as spin-orbit torque wiring to generate spin Hall effect, then magnetization reversal can be achieved, but electrical resistivity is high leading to high power consumption
Solution Approach 1:
The patent employs a composite spin-orbit torque wiring structure consisting of a Cu layer (low resistivity) and a Ta layer (high spin Hall effect) laminated together. The Cu layer provides low electrical resistance to reduce power consumption, while the Ta layer generates the necessary spin Hall effect for magnetization reversal. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent applies different material properties to different layers of the spin-orbit torque wiring. The Cu layer is optimized for electrical conduction (low resistivity) while the Ta layer is optimized for spin Hall effect generation. By assigning specific functional qualities to specific locations (layers), the system achieves both low power consumption and effective magnetization reversal.
2Use of energy by moving object
If spin-orbit torque wiring is made thinner to reduce resistance, then power consumption decreases, but lattice matching with ferromagnetic metal layer becomes difficult
Solution Approach 1:
The composite Cu-Ta structure allows optimization of each layer's thickness independently. The Ta layer can be kept thin enough to maintain lattice matching with the ferromagnetic metal layer, while the Cu layer provides the necessary electrical conduction path. This composite approach enables thin overall structure for low power consumption without compromising lattice matching.
3Reliability
If both spin Hall effect and interface Rashba effect are utilized to reduce reversal current density, then magnetization reversal efficiency improves, but device complexity increases
Solution Approach 1:
The Cu-Ta composite wiring structure naturally provides both spin Hall effect (from Ta) and interface Rashba effect (at the Cu-Ta interface and Cu-ferromagnetic interface). This single composite structure achieves dual effects without requiring separate wiring structures, thus improving magnetization reversal efficiency while limiting the increase in device complexity.
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 effectively produces both spin Hall and interface Rashba effects, reducing power consumption and achieving a low-resistance spin-orbit torque wiring with improved lattice matching, enabling efficient magnetization reversal with lower current densities.
Implementation Method 1
A magnetization reversal method in which a pure spin current generated by a spin Hall effect is utilized as a means for reducing the reversal current in a mechanism that is different from an STT
Implementation Method 2
it is required to effectively produce both the spin Hall effect and an interface Rashba effect that occurs at an interface between different materials
Data Source
Figure 1A~2
Figure 3A~3B
Figure 4
AI summary
This spin current magnetization rotational element includes a first ferromagnetic metal layer for a magnetization direction to be changed, and a spin-orbit torque wiring extending in a second direction intersecting a first direction which is an orthogonal direction to a surface of the first ferromagnetic metal layer and configured to be joined to the first ferromagnetic metal layer, wherein the spin-orbit torque wiring has a structure in which a spin conduction layer joined to the first ferromagnetic metal layer and a spin generation layer joined to the spin conduction layer on a surface on a side opposite to the first ferromagnetic metal layer are laminated.