Heusler Multilayer MRAM for Low-Current Perpendicular Anisotropy

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Solution Overview

Problem

Current MRAM devices using magnetic tunnel junctions with cobalt-iron-boron alloys for magnetic layers require high switching currents due to interfacial perpendicular magnetic anisotropy, limiting device scalability and thermal stability.

Innovation Solution

Employing multilayer structures of two half metallic Heusler compounds with broken cubic symmetry to achieve volume perpendicular magnetic anisotropy, allowing for lower switching currents and higher tunnel magnetoresistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cobalt-iron-boron alloys are used for magnetic layers in MRAM devices, then perpendicular magnetic anisotropy is achieved, but switching current becomes excessively high

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoidswitching current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent employs composite multilayer structures combining half-metallic Heusler compounds (such as Co2MnSi, Co2MnGe, Mn2CoAl) with non-magnetic spacer layers (such as Mn3Ge, Mn3Al). This composite approach creates volume perpendicular magnetic anisotropy through the broken cubic symmetry in the Heusler layers, while the non-magnetic spacers reduce magnetization and thus switching current requirements, resolving the contradiction between achieving PMA and reducing switching current.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the fundamental parameter of magnetic anisotropy origin from interfacial (in conventional CoFeB structures) to volume-based through the use of half-metallic Heusler compounds with broken cubic symmetry. This parameter change enables simultaneous achievement of perpendicular magnetic anisotropy and reduced switching current by decoupling the anisotropy mechanism from the magnetization magnitude.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If interfacial perpendicular magnetic anisotropy is used, then magnetic stability is achieved, but device scalability is limited

Engineering Contradiction:

Improvemagnetic stabilityVSAvoiddevice scalability

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent transitions from interfacial magnetic anisotropy to volume magnetic anisotropy by using half-metallic Heusler compounds with broken cubic symmetry. This parameter change enables better scalability because volume anisotropy is intrinsic to the material bulk rather than dependent on interface quality, allowing more consistent performance across devices of varying sizes and fabrication tolerances.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If high spin polarization is achieved, then tunnel magnetoresistance increases, but switching current also increases

Engineering Contradiction:

Improvetunnel magnetoresistanceVSAvoidswitching current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent uses composite structures where half-metallic Heusler layers provide high spin polarization (0.6-1.0) for high TMR, while non-magnetic spacer layers (Mn3Ge, Mn3Al) reduce the overall magnetization of the magnetic tunnel junction. This composite design decouples the relationship between spin polarization and magnetization magnitude, enabling high TMR with reduced switching current.

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

The multilayer structures enable MRAM devices with high spin polarization, high ON/OFF ratio, and low magnetization, facilitating device scaling and improved thermal stability with reduced switching currents.

Implementation Method 1

the half metallic Heusler multilayer structure being located outward of the templating layer and exhibiting perpendicular magnetic anisotropy (PMA)

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Implementation Method 2

High spin polarization, and thus high TMR, is desirable (higher TMR provides a higher ON/OFF ratio)

Methodology Applied

Scientific EffectSpin polarization: Polarisation

Implementation Method 3

The resistance changes based on the magnetic orientation of the two magnetic layers, and the relative change in resistance is referred to as the tunnel magnetoresistance (TMR)

Methodology Applied

Scientific EffectTunnel magnetoresistance: Magnetoresistance

Implementation Method 4

The current delivers spin angular momentum, so that once a threshold current is exceeded, the direction of the memory layer moment is switched. Since these MRAM devices are switched using Spin Transfer Torque (STT)

Methodology Applied

Scientific EffectSpin transfer torque: Angular Momentum

Data Source

PatentUS12581868B2Half metallic Heusler multilayers with perpendicular magnetic anisotropy

Publication Date: 2026.03.17 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetoresistive random-access memory cell includes a templating layer, including a binary alloy having an alternating layer lattice structure, and a half metallic Heusler multilayer structure including a plurality of layers of two different Heusler compounds, at least one of which is half metallic. The half metallic Heusler multilayer structure is located outward of the templating layer and exhibits perpendicular magnetic anisotropy (PMA). A tunnel barrier is outward of the half metallic Heusler multilayer structure, and a magnetic layer is outward of the tunnel barrier.