Acute-Angle SOT Magnetic Tunnel Junctions for Field-Free MRAM Writing

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Solution Overview

Problem

The performance of magnetic random access memories (MRAMs) needs to be improved, particularly in terms of read-write speed and the need for external magnetic fields during write operations.

Innovation Solution

A magnetic random access memory cell design featuring a spin-orbit torque (SOT) layer with a write current direction parallel to it and a magnetic tunnel junction with symmetrical substructures forming an acute angle with the write current direction, allowing for both magnetic moment components in the same direction, enabling write operations without external magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a conventional SOT-MRAM structure with perpendicular magnetic moment is used, then the read-write speed is improved and write current is reduced, but external magnetic fields are still required for write operations

Engineering Contradiction:

Improveread-write speedVSAvoidrequirement for external magnetic field

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by designing the magnetic tunnel junction with a specific magnetic moment orientation that forms an acute angle with the write current direction, rather than using the conventional perpendicular arrangement. This asymmetric configuration enables the spin-orbit torque to effectively reverse the magnetic moment without requiring external magnetic fields, thus resolving the contradiction between improved read-write speed and device complexity

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the magnetic moment orientation parameter from perpendicular to acute angle relative to the write current direction. This parameter change optimizes the interaction between the spin-orbit torque and the magnetic moment, enabling efficient write operations without external magnetic fields while maintaining high read-write speed

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the magnetic moment direction is perpendicular to the write current direction, then the structure is simplified, but write operations require external magnetic fields which increases complexity

Engineering Contradiction:

Improvemagnetic tunnel junction structureVSAvoidwrite operation process

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The patent uses asymmetry by setting the magnetic moment direction at an acute angle to the write current direction rather than perpendicular. This asymmetric arrangement optimizes the torque efficiency for magnetic moment reversal, eliminating the need for external magnetic fields during write operations and thereby improving ease of operation

Inventive Principle:

Principle #4Asymmetry

3Ease of operation

If symmetrical substructures with acute angle magnetic moment are used, then external magnetic field requirement is eliminated, but the manufacturing precision requirement increases

Engineering Contradiction:

Improvewrite operation without external magnetic fieldVSAvoidsubstructure symmetry and angle precision

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent specifies the magnetic moment direction parameter as forming an acute angle with the write current direction, which optimizes the balance between operational simplicity and manufacturability. This parameter setting enables write operations without external magnetic fields while maintaining reasonable manufacturing precision requirements through proper structural design

Inventive Principle:

Principle #35Parameter changes

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 design enhances read-write speed and simplifies the MRAM structure by allowing magnetic moment reversal using the SOT layer alone, improving overall MRAM performance and simplifying production.

Implementation Method 1

The SOT-based MRAM adopts a three-terminal magnetic tunnel junction structure, and has separate paths for read and write, so the write current is greatly reduced... the write current, relying on the current flowing in the material parallel to and adjacent to the free layer, drives the torque generated by the spin orbit effect on their interface to reverse the magnetic moment of the free layer

Methodology Applied

Scientific EffectSpin-orbit coupling:

Data Source

PatentUS12387773B2Magnetic random access memory cell and memory

Publication Date: 2025.08.12 SEMICON MFG INT (SHANGHAI) CORP

AI summary

Provided are a magnetic random access memory cell and a magnetic random access memory. One form of a memory cell includes: a spin-orbit torque (SOT) layer, through which a write current flows when performing a write operation on the magnetic random access memory cell, a direction of the write current being a first direction, and a direction parallel to the SOT layer and perpendicular to the first direction being a second direction; and a magnetic tunnel junction, located on the SOT layer, the magnetic tunnel junction including substructures symmetrical with respect to the second direction, and a magnetic moment direction of the substructure forming an acute included angle with the first direction.