Topological Insulator SOT Generator for Magnetic Memory Switching

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Solution Overview

Problem

Current methods for manipulating magnetization in magnetic memory devices, such as STT-MRAM, require high current densities that are close to the breakdown limit, leading to potential device damage, and existing spin-orbit torque (SOT) generation techniques also require large charge currents, necessitating a more efficient and reliable approach.

Innovation Solution

The use of topological insulator materials as a spin-orbit torque generator layer in conjunction with ferromagnetic memory layers with perpendicular magnetic anisotropy, allowing for efficient SOT generation with reduced operating currents, eliminating the need for external magnetic fields and minimizing energy consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spin-transfer torque (STT) is used to switch magnetization, then magnetization switching can be achieved, but high current density (>10^7 A/cm^2) is required which is close to the breakdown limit

Engineering Contradiction:

Improvedevice reliabilityVSAvoidcurrent density

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent introduces a topological insulator layer as an intermediary between the charge current source and the ferromagnetic layer. This intermediary generates spin-orbit torque that acts on the magnetization without requiring high current density through the magnetic layers, thus resolving the contradiction between achieving magnetization switching and maintaining device reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the direct spin-transfer torque mechanism (which requires high current through magnetic layers) with a spin-orbit torque mechanism generated by topological insulators. This substitution changes the physical mechanism from direct mechanical momentum transfer to orbital-to-spin angular momentum conversion, reducing the harmful current density requirement

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If heavy metal layers are used for spin-orbit torque generation, then magnetization switching can be achieved without charge current through FM layer, but large charge current (10^7 A/cm^2) is still required in the HM layer

Engineering Contradiction:

Improvemagnetic memory unit integrityVSAvoidcharge current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the material parameter of the spin-orbit torque generator from conventional heavy metals to topological insulators, which have fundamentally different electronic band structures and spin-orbit coupling properties. This parameter change enables more efficient spin current generation with lower charge current input

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure combining topological insulator material with ferromagnetic layers, where the topological insulator's unique surface state electrons provide enhanced spin-orbit coupling efficiency. This composite approach leverages the complementary properties of different materials to achieve superior performance

Inventive Principle:

Principle #40Composite materials

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 solution significantly reduces the critical current density required for magnetization switching, enhancing the reliability and energy efficiency of magnetic memory devices while avoiding damage from high charge currents.

Implementation Method 1

using electric currents to manipulate magnetic units through spin-orbit torque, which in particular, originates from strong spin-orbit interactions hosted by topological insulators

Methodology Applied

Scientific EffectSpin-orbit torque:

Implementation Method 2

sensing electrodes configured to measure a Hall effect of the magnetic memory layer

Methodology Applied

Scientific EffectHall effect: Hall Effect

Data Source

PatentUS10559747B1Topological insulator-based high efficiency switching of magnetic unit, method and applications

Publication Date: 2020.02.11 JOHNS HOPKINS UNIVERSITY

AI summary

A magneto-electronic device may include: a spin-orbit torque (SOT) generator layer; a magnetic memory layer; and/or sensing electrodes configured to measure a Hall effect of the magnetic memory layer. The SOT generator layer may include topological insulator material, and the magnetic memory layer may include ferromagnetic material with perpendicular magnetic anisotropy. A magneto-electronic device may include: a spin-orbit torque (SOT) generator layer; a first magnetic memory layer on the SOT generator layer; an insulating layer on the first magnetic memory layer; and/or a second magnetic memory layer on the insulating layer. The SOT generator layer may include topological insulator material. The first magnetic memory layer and the second magnetic memory layer may include ferromagnetic material with either perpendicular magnetic anisotropy or in-plane magnetic anisotropy.