Ferromagnetic Free Layer Symmetry Breaking for Field-Free SOT Switching
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Solution Overview
Problem
Magnetic memories using spin orbit torque require additional heavy metal layers and magnetic fields to ensure deterministic magnetization reversal, resulting in complex structures.
Innovation Solution
A ferromagnetic free layer with a magnetic film alloy of laminated films, where the thickness of each film decreases gradually, breaking in-plane and out-of-plane structural symmetries, allowing for deterministic magnetization reversal driven by spin orbit torque without additional heavy metal layers or magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If spin orbit torque is used to drive magnetization reversal, then the service life of magnetic memories can be prolonged by separating storage and reading paths, but additional heavy metal layers and magnetic fields are required, resulting in complex structure
Solution Approach 1:
The patent combines the heavy metal layer and ferromagnetic free layer into a single CoFeB layer with DMI interaction, merging the functions of spin current generation and magnetization reversal into one material system, thereby eliminating the need for separate heavy metal layers and external magnetic fields
Solution Approach 2:
The CoFeB layer serves multiple functions simultaneously: it acts as both the ferromagnetic layer and the source of spin current through its intrinsic DMI interaction, enabling the layer to perform both storage and the torque-generating functions that previously required separate components
2Reliability
If additional heavy metal layer is added to provide spin current, then deterministic magnetization reversal can be achieved, but the structure becomes complex
Solution Approach 1:
The CoFeB layer generates its own spin current through intrinsic DMI interaction without requiring an external heavy metal layer, making the system self-sufficient and eliminating additional structural components while maintaining deterministic magnetization reversal
3Reliability
If additional magnetic field is applied along current direction, then deterministic magnetization reversal can be ensured, but the structure and control become complex
Solution Approach 1:
The DMI interaction within the CoFeB layer automatically provides the necessary chiral spin texture that enables deterministic magnetization reversal without requiring external magnetic fields, simplifying both the device structure and the control mechanism
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
Simplifies the structure of magnetic tunnel junctions and memories by enabling deterministic magnetization reversal with a pure current, suitable for high-density, low-power magnetic memories.
Implementation Method 1
the spin orbit torque can be designed as a three-terminal storage unit to separate the storage and reading paths of information and prolong the service life of the magnetic memories
Implementation Method 2
the thickness of each of the films decreases successively from a first end to a second end of the magnetic film alloy... breaking in-plane and out-of-plane structural symmetries
Data Source
AI summary
A ferromagnetic free layer, a preparation method and an application thereof are provided, where the ferromagnetic layer includes a magnetic film alloy, and the magnetic film alloy includes multiple layers of laminated films. A thickness of each of the films decreases gradually from a first end to a second end of the magnetic film alloy, so as to break in-plane structural symmetry of the magnetic film alloy, and the films include heavy metal films and ferromagnetic metal films, where out-of-plane crystal symmetry of the magnetic film alloy is broken by means of component gradients. When a current is applied in plane of the magnetic film alloy, a spin orbit torque will be generated, which directly drives the magnetic moment of the magnetic film alloy to undergo a deterministic magnetization reversal.