Spin-Transfer Torque MRAM Reducing Writing Current
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Solution Overview
Problem
Miniaturization of MRAM devices leads to insufficient electric current passing through address wiring lines, affecting the stability and efficiency of magnetization reversal, while reducing the saturation-magnetization level compromises thermal stability.
Innovation Solution
A memory device with a memory layer and a fixed-magnetization layer separated by an insulating intermediate layer, where the magnetization direction is reversed by injecting a spin-polarized electron, reducing the effective demagnetizing field and maintaining a sufficient saturation-magnetization level to ensure thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the device is miniaturized to increase integration density, then the area of the memory device is reduced, but the electric current passing through address wiring lines becomes insufficient
Solution Approach 1:
The patent replaces the conventional current-magnetic field method (using address wiring lines to generate magnetic fields) with a spin injection method. Instead of relying on electrical current flowing through wiring lines to create magnetic fields for magnetization reversal, the invention uses spin-polarized electrons injected directly into the memory layer through a magnetic tunnel junction, eliminating the need for high current through address wiring lines and solving the problem of insufficient current in miniaturized devices
Solution Approach 2:
The patent changes the fundamental parameter of magnetization reversal from field-induced (using external magnetic fields from wiring lines) to current-induced spin transfer torque. By changing the mechanism from Lenz's law-based magnetic field generation to direct spin injection, the system achieves magnetization reversal with much lower current requirements, enabling device miniaturization without compromising switching capability
2Power
If the saturation-magnetization level is reduced to facilitate magnetization reversal, then the writing current is reduced, but the thermal stability deteriorates
Solution Approach 1:
The patent changes the mechanism of magnetization reversal from field-induced to spin transfer torque-induced, which fundamentally alters the relationship between magnetization parameters and switching current. By using spin-polarized electron injection, the system achieves efficient magnetization reversal without requiring reduced saturation magnetization, thereby maintaining both low writing current and high thermal stability simultaneously
Solution Approach 2:
The patent introduces spin-polarized electrons as an intermediary mechanism for magnetization reversal. Instead of directly applying magnetic fields or relying on thermal effects, the spin injection acts as a mediator that transfers angular momentum from electrons to the magnetic moment of the memory layer, enabling controlled reversal with low current while preserving the intrinsic thermal stability of the high saturation-magnetization material
3Power
If the effective demagnetizing field is reduced to improve magnetization reversal efficiency, then the writing current is reduced, but the structure complexity increases
Solution Approach 1:
The patent changes the fundamental approach to magnetization reversal from external field application to internal spin transfer torque generation. By changing the mechanism from field-induced reversal (requiring complex wiring and field control) to spin injection through a magnetic tunnel junction, the system achieves reduced writing current while actually simplifying the overall device structure by eliminating the need for complex address wiring line configurations
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 stable magnetization reversal with reduced writing electric current, enhancing thermal stability and reducing power consumption while maintaining high saturation-magnetization levels, thus preventing operation errors and achieving reliable memory operation.
Implementation Method 1
information is recorded on the memory layer with a change in magnetization direction of the memory layer caused by injecting a spin-polarized electron in a stacked direction
Data Source
AI summary
A memory device is provided. The memory device includes a memory layer and a fixed-magnetization layer. The memory layer retains information based on a magnetization state of a magnetic material. The fixed-magnetization layer is formed on the memory layer through an intermediate layer made of an insulating material. The information is recorded on the memory layer with a change in a magnetization direction of the memory layer caused by injecting a spin-polarized electron in a stacked direction. A level of effective demagnetizing field, which is received by the memory layer, is smaller than a saturation-magnetization level of magnetization of the memory layer.