Magnetoresistive Element With Composite Storage Layer

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Solution Overview

Problem

Current magnetoresistive elements with perpendicular magnetization structures face challenges in reducing saturation magnetization and magnetic relaxation constants to achieve low-switching current spin transfer torque writing while maintaining thermal stability and small element size.

Innovation Solution

A magnetoresistive element is designed with a structure that includes a storage layer with alternately laminated magnetic and nonmagnetic materials, such as CoFeB and Ta/W, and a conductive layer, which reduces saturation magnetization and magnetic relaxation constants, enabling low-switching current magnetization reversal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If material composition is adjusted to reduce saturation magnetization Ms, then switching current is reduced, but thermal stability may be compromised

Engineering Contradiction:

Improveswitching currentVSAvoidthermal stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The storage layer uses a composite structure of CoFeB (magnetic material) and Ta/W (nonmagnetic material) laminated alternately. This composite structure reduces the saturation magnetization Ms of the storage layer while maintaining perpendicular magnetic anisotropy, enabling low switching current operation. The nonmagnetic Ta/W layers act as spacers that reduce magnetic interaction and lower the overall Ms without compromising the perpendicular magnetization structure needed for thermal stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the magnetic parameters of the storage layer by adjusting the composition ratio and thickness of CoFeB and Ta/W layers. By optimizing these parameters, the saturation magnetization Ms is reduced to achieve lower switching current, while the perpendicular magnetic anisotropy energy is maintained through careful control of layer thicknesses and materials, ensuring thermal stability is preserved.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If element size is reduced to increase storage density, then switching current typically increases, but perpendicular magnetization structure enables size reduction while maintaining low switching current

Engineering Contradiction:

Improveelement sizeVSAvoidswitching current

Core Design Contradiction:

Volume of moving objectVSUse of energy by moving object

Solution Approach 1:

The alternating lamination of CoFeB and Ta/W creates a composite magnetic structure where the Ta/W nonmagnetic layers reduce magnetic damping and facilitate magnetization switching. This composite structure enables perpendicular magnetization with reduced switching current, allowing element size to be reduced for higher storage density without the switching current increasing proportionally.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The storage layer structure is optimized locally by placing Ta/W nonmagnetic layers between CoFeB magnetic layers. This local structural modification creates regions with reduced magnetic interaction and lower effective anisotropy, enabling easier magnetization switching in smaller elements while maintaining the perpendicular magnetization direction needed for high storage density.

Inventive Principle:

Principle #3Local quality

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 proposed structure allows for efficient magnetization switching at a low current while maintaining thermal stability and reducing element size, enhancing the performance of spin transfer torque write systems.

Implementation Method 1

a write (spin transfer torque write) system using spin momentum transfer (SMT) is proposed

Methodology Applied

Scientific EffectSpin transfer torque (SMT):

Implementation Method 2

Magnetoresistive element having a ferromagnetic tunnel junction

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 3

a material having large perpendicular magnetocrystalline anisotropy is employed in order to realize both smaller element size and lower switching current while a thermal stability is maintained

Methodology Applied

Scientific EffectMagnetocrystalline anisotropy:

Data Source

PatentUS9312475B2Magnetoresistive element, magnetic memory, and method of manufacturing magnetoresistive element

Publication Date: 2016.04.12 KIOXIA CORP

AI summary

According to one embodiment, a magnetoresistive element includes first and second magnetic layers, a first nonmagnetic layer, a conductive layer. The first and second magnetic layers have axes of easy magnetization perpendicular to a film plane. The first and second magnetic layers have variable and invariable magnetization directions, respectively. The first nonmagnetic layer is between the first and second magnetic layers. The conductive layer is on a surface of the first magnetic layer opposite to a surface on which the first nonmagnetic layer is formed. The first magnetic layer has a structure obtained by alternately laminating magnetic and nonmagnetic materials. The nonmagnetic material includes at least one of Ta, W, Nb, Mo, Zr, Hf. The magnetic material includes Co and Fe. One of the magnetic materials contacts the first nonmagnetic layer. One of the nonmagnetic materials contacts the conductive layer.