Spin Current Magnetization Reversal Element With Inclined Surface
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Solution Overview
Problem
Existing methods for magnetization reversal in TMR elements require high reversal current density and external magnetic fields, which can lead to data noise and integration issues due to the difficulty in controlling oxygen content and unintentional magnetization reversal.
Innovation Solution
A spin current magnetization reversal element is designed with inclined surfaces on ferromagnetic metal layers to generate a symmetry break, allowing magnetization reversal by spin-orbit torque without an external magnetic field, achieved through the stacking of ferromagnetic metal layers and spin-orbit torque wiring with inclined surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If magnetization reversal is achieved using spin transfer torque (STT) by passing current through the stacking direction, then energy efficiency is improved, but the reversal current density becomes high which reduces element lifespan
Solution Approach 1:
The patent replaces the direct spin transfer torque mechanism (which requires high current through the element) with a spin-orbit torque mechanism using the spin Hall effect. A heavy metal layer generates spin current that acts on the ferromagnetic layer from the side, substituting the direct current-through-element mechanism with a side-coupled spin current mechanism, thereby reducing the harmful current density while maintaining energy efficiency.
Solution Approach 2:
The patent introduces a heavy metal layer as an intermediary between the current path and the ferromagnetic layer. This intermediary generates the spin-orbit torque needed for magnetization reversal without requiring high current to pass through the magnetoresistance element itself, thus protecting the element while achieving the desired magnetic switching.
2Device complexity
If magnetization reversal uses spin-orbit torque without external magnetic field, then integration is improved, but symmetry breaking becomes difficult without magnetic field source
Solution Approach 1:
The patent introduces structural asymmetry by creating an inclined surface on the ferromagnetic layer. This geometric asymmetry breaks the magnetic symmetry without requiring an external magnetic field, allowing the spin-orbit torque to effectively switch magnetization. The inclined surface creates different magnetic anisotropy conditions that enable symmetry breaking inherently through the material structure rather than external fields.
Solution Approach 2:
The patent changes the geometric parameter of the ferromagnetic layer by creating an inclined surface with a specific angle. This parameter change (from flat to inclined) fundamentally alters the magnetic anisotropy and symmetry properties of the layer, enabling spin-orbit torque to break symmetry and achieve magnetization reversal without external magnetic field assistance.
3Ease of operation
If oxygen content in oxide film is altered to break magnetization symmetry, then magnetization reversal without magnetic field becomes possible, but control difficulty increases leading to manufacturing precision issues
Solution Approach 1:
The patent changes a geometric parameter (surface inclination angle) instead of a chemical parameter (oxygen content). This geometric modification achieves the same symmetry-breaking effect required for magnetization reversal but is much more controllable and precise in manufacturing processes, avoiding the difficulties of controlling oxygen content in oxide films.
Solution Approach 2:
The patent applies local geometric modification by creating an inclined surface on the ferromagnetic layer. This local structural change (inclination) creates the necessary symmetry breaking at the specific location where it is needed, while maintaining precise control over the inclination angle through manufacturing processes, avoiding the uniform but difficult-to-control oxygen content modification approach.
4Ease of operation
If external magnetic field is applied for magnetization reversal, then symmetry breaking is achieved, but data noise increases due to unintentional magnetization reversal
Solution Approach 1:
The patent uses structural asymmetry (inclined surface) to break magnetic symmetry, replacing the external magnetic field approach. This asymmetric geometry provides the necessary symmetry breaking for spin-orbit torque to work while being spatially localized and controllable, preventing the widespread unintentional magnetization reversal that causes data noise when using external magnetic fields.
Solution Approach 2:
The inclined surface acts as an intermediary that enables symmetry breaking without external magnetic fields. This structural feature mediates between the spin-orbit torque and the magnetization, providing the necessary symmetry breaking in a controlled, localized manner that avoids the data noise problems associated with external magnetic field approaches.
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 approach enables magnetization reversal without external magnetic fields, reducing data noise and improving integration by maintaining consistent magnetization stability and preventing unintentional magnetization reversal, thus enhancing the long-term storage and integration of spin current magnetization reversal elements.
Implementation Method 1
much attention has been focused on magnetization reversal that utilizes pure spin current generated by spin-orbit interaction as a technique for reducing the reversal current (for example, see Patent Document 1). Pure spin current generated by spin-orbit interaction induces spin-orbit torque (SOT), with this SOT causing magnetization reversal.
Implementation Method 2
When the symmetry of the magnetization strength is broken, magnetization rotation becomes easier, and magnetization reversal using SOT becomes possible even in the absence of a magnetic field.
Data Source
AI summary
This spin current magnetization reversal element includes a magnetoresistance effect element having a first ferromagnetic metal layer having a fixed magnetization direction, a second ferromagnetic metal layer having a variable magnetization direction, 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 first direction that intersects the stacking direction of the magnetoresistance effect element, and contacts the surface of the magnetoresistance elect element on the side facing the second ferromagnetic metal layer, wherein at least one surface of the second ferromagnetic metal layer in the stacking direction has an inclined surface that is inclined in the first direction, and the direction of magnetization of the second ferromagnetic metal layer is inclined due to the inclined surface.