Columnar 3D Magnetic Storage for Field-Free SOT Writing
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Solution Overview
Problem
Existing three-dimensional magnetic storage devices face challenges in achieving high storage density due to large area occupation and thermal instability, particularly in the XY plane, and require additional magnetic fields for perpendicular magnetization reversal, increasing complexity and energy consumption.
Innovation Solution
A columnar three-dimensional magnetic storage unit utilizing SOT-induced precessional magnetization reversal with a central nanopillar and magnetic layers, where the magnetization direction is axially oriented, allowing for smaller area occupation and reduced power consumption, and a writing method that applies current pulses to switch between low and high resistance states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If SOT-MRAM uses three terminals per unit to enable spin-orbit torque reversal, then magnetic torque reversal is achieved, but the area occupied by each unit increases
Solution Approach 1:
The patent implements a nested structure where the magnetic free layer is positioned inside the magnetic pinned layer, both sharing a common central nanopillar. This nested arrangement allows both magnetic layers to be integrated within a single unit cell, reducing the overall area occupation while maintaining the three-terminal SOT-MRAM structure for effective magnetic torque reversal.
Solution Approach 2:
The central nanopillar serves multiple functions simultaneously: it acts as the spin-orbit coupling material for generating spin current, provides the structural core for both magnetic layers, and functions as the common electrode terminal. This multi-functionality reduces the number of separate components needed, thereby reducing unit area occupation.
2Stability of the object's composition
If additional magnetic field is applied to achieve perpendicular magnetization reversal, then out-of-plane magnetic torque reversal is enabled, but structural complexity and energy consumption increase
Solution Approach 1:
The patent changes the magnetization orientation parameter from in-plane to out-of-plane (perpendicular) direction by designing the magnetic layers with appropriate anisotropy. This parameter change enables the magnetic free layer to achieve stable perpendicular magnetization states without requiring external magnetic fields, thereby reducing structural complexity and energy consumption while maintaining thermal stability.
Solution Approach 2:
The magnetic layers are designed with intrinsic perpendicular magnetic anisotropy that enables self-driven magnetization reversal without external assistance. The spin-orbit torque from the central nanopillar directly induces perpendicular magnetization reversal in the magnetic free layer, making the system self-sufficient and eliminating the need for additional magnetic field generation structures.
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 solution enhances write speed and reduces power consumption while increasing storage density by minimizing area occupation in the XY plane and eliminating the need for external magnetic fields, achieving efficient data switching through SOT-induced precessional magnetization reversal.
Implementation Method 1
the current in the heavy metal layer or topological insulator layer is converted into a spin current through spin-orbit coupling and injected into the free layer, driving the reversal of the magnetic torque in the magnetic free layer
Implementation Method 2
A columnar three-dimensional magnetic storage unit utilizing SOT-induced precessional magnetization reversal with a central nanopillar and magnetic layers
Implementation Method 3
When the magnetization direction of the FL is parallel to that of the PL, the MTJ exhibits a low resistance state (LRS)... Conversely, if the magnetization direction of the FL is opposite to that of the PL, the MTJ exhibits a high resistance state (HRS)
Data Source
AI summary
A columnar three-dimensional magnetic storage unit and a writing method are disclosed. In the magnetic storage unit, a central nanopillar is a nanopillar structure made of a material having a spin-orbit coupling effect; a magnetic storage layer wraps an outer side of the central nanopillar; a magnetic free layer surrounds and contacts the central nanopillar, with a polarization direction of the magnetic free layer extending axially along the nanopillar structure, and the magnetization reversal of the magnetic free layer depending on spin-polarized electrons, whose polarization direction is circumferential, generated by the central nanopillar, a damping-like torque and a field-like torque generated by the spin-polarized electrons synergistically achieving the magnetization precessional reversal of the magnetic free layer; a magnetic tunneling layer wraps an outer side of the magnetic free layer; a magnetic pinned layer wraps an outer side of the magnetic tunneling layer.