Spin-Orbit Torque MRAM Switching to Lower Write Current

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Solution Overview

Problem

Existing spin-torque magnetic memory devices require significant write currents to switch the magnetic state of free layers, leading to potential breakdown of magnetic tunnel junctions over time.

Innovation Solution

The use of spin-orbit torque (SOT) current in conjunction with spin-transfer torque (STT) to assist in switching the magnetic state of the free layer, reducing the necessary write current and minimizing tunnel junction breakdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spin-transfer torque (STT) is used to switch the magnetic state of the free layer, then the magnetic state can be changed, but the write current magnitude is significant and leads to breakdown of the magnetic tunnel junction over time

Engineering Contradiction:

Improvemagnetic tunnel junction durabilityVSAvoidwrite current magnitude

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

A spin-orbit torque (SOT) segment is introduced as an intermediary component adjacent to the free layer. This SOT segment receives a portion of the write current and generates spin current that acts on the free layer's magnetization, reducing the burden on the magnetic tunnel junction and lowering the overall write current requirement while improving reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent combines spin-orbit torque (SOT) and spin-transfer torque (STT) mechanisms into a hybrid switching approach. The SOT segment and the magnetic tunnel junction work together synergistically, where the SOT provides initial spin torque and the STT completes the switching, achieving more efficient and reliable magnetic state transitions

Inventive Principle:

Principle #5Merging (Combining)

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 combination of SOT and STT results in more efficient switching of the free layer, reducing the amount of write current required and lowering the risk of tunnel junction breakdown, thereby promoting long-term functionality of memory devices.

Implementation Method 1

a spin-orbit torque (SOT) segment on a sidewall of the free layer. The spin current is injected into the free layer in a direction perpendicular to the boundary where the free layer and the conductor meet

Methodology Applied

Scientific EffectSpin Hall Effect: Hall Effect

Implementation Method 2

Writing spin-torque magnetic memory cells can be accomplished by sending a write current through the memory device where the spin angular momentum carried by the current between the reference and free layers can change the magnetic state of the free layer

Methodology Applied

Scientific EffectSpin-Transfer Torque:

Data Source

PatentUS12317753B2Magnetic memory using spin-orbit torque

Publication Date: 2025.05.27 EVERSPIN TECHNOLOGIES INC

AI summary

Spin-orbit-torque (SOT) segments are provided along the sides of free layers in magnetoresistive devices that include magnetic tunnel junctions. Current flowing through such SOT segments injects spin current into the free layers such that spin torque is applied to the free layers. The spin torque can be used as an assist to spin-transfer torque generated by current flowing vertically through the magnetic tunnel junction in order to improve the efficiency of the switching current applied to the magnetoresistive device.