Multiferroic Layer Crystalline Phase Modulation for Spin Polarizability

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Solution Overview

Problem

Existing magnetoresistive effect elements face challenges in stably recording data with multiple values due to insufficient electric field generation and magnetization anisotropy, leading to instability in data recording.

Innovation Solution

A laminated structure comprising a ferromagnetic layer and a multiferroic layer with specific crystalline phases, where the multiferroic layer has regions with rhombohedral and tetragonal crystalline phases, enhancing both ferromagnetic and ferroelectric characteristics to stabilize spin polarizability modulation by an electric field.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single-phase multiferroic layer is used, then the structure is simple, but the electric field generation and magnetization anisotropy are insufficient leading to unstable data recording

Engineering Contradiction:

Improvedata recording stabilityVSAvoidcrystalline phase structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The multiferroic layer is designed with different crystalline phases in different regions: a first region with rhombohedral phase providing strong magnetization anisotropy, and a second region with tetragonal phase providing strong electric field generation through dielectric polarization. This local differentiation of material properties resolves the contradiction by making each region specialized for its function while maintaining overall structural integrity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses a composite multiferroic layer containing multiple crystalline phases (rhombohedral and tetragonal) within the same material system. This composite structure combines the advantages of both phases: the rhombohedral phase contributes to stable magnetization through strong anisotropy, while the tetragonal phase enhances electric field generation, thereby improving data recording stability without requiring entirely separate layers.

Inventive Principle:

Principle #40Composite materials

2Power

If the multiferroic layer has strong dielectric polarization, then electric field generation is enhanced, but magnetization anisotropy may be insufficient

Engineering Contradiction:

Improveelectric field strengthVSAvoidmagnetization stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Different regions of the multiferroic layer are assigned different crystalline phases optimized for specific functions: the tetragonal phase region (second region) provides strong dielectric polarization and electric field generation, while the rhombohedral phase region (first region) provides strong magnetization anisotropy and stability. This spatial separation of functions resolves the contradiction between enhancing electric field strength and maintaining magnetization stability.

Inventive Principle:

Principle #3Local quality

3Reliability

If the multiferroic layer has strong magnetization anisotropy, then spin polarizability is well-defined, but electric field generation may be insufficient

Engineering Contradiction:

Improvespin polarizability definitionVSAvoidelectric field strength

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The multiferroic layer is structured with rhombohedral phase regions that provide strong magnetization anisotropy for well-defined spin polarizability, and tetragonal phase regions that provide strong dielectric polarization for enhanced electric field generation. This local functional differentiation allows each phase to optimize its contribution without compromising the other.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

By creating a composite multiferroic layer with both rhombohedral and tetragonal phases, the invention simultaneously achieves strong magnetization anisotropy (from rhombohedral phase) and strong electric field generation (from tetragonal phase), resolving the contradiction between these two requirements.

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 proposed structure enables stable modulation of spin polarizability, increasing the difference in resistance values and allowing for clear multivalued data recording, improving the reliability of magnetoresistive effect elements.

Implementation Method 1

modulating spin polarizabilities of ferromagnetic layers using electric fields

Methodology Applied

Scientific EffectDielectric polarization: Dielectric

Implementation Method 2

stable modulation of spin polarizability of a ferromagnetic material by an electric field

Methodology Applied

Scientific EffectSpin polarizability modulation:

Implementation Method 3

the anisotropy of the magnetization of a ferromagnetic layer is not sufficient

Methodology Applied

Scientific EffectMagnetization anisotropy: Anisotropy

Implementation Method 4

a surface of the multiferroic layer on the ferromagnetic layer side has a first region, a crystalline phase of which is rhombohedral, and a second region, a crystalline phase of which is tetragonal

Methodology Applied

Scientific EffectCrystalline phase structure: Crystallisation

Implementation Method 5

magnetoresistive effect elements such as giant magnetoresistance (GMR) elements constituted of a multilayer film of a ferromagnetic layer and a nonmagnetic layer

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Data Source

PatentUS10461244B2Laminated structure and spin modulation element

Publication Date: 2019.10.29 TDK CORP

AI summary

A laminated structure according to an embodiment includes: a ferromagnetic layer; and a multiferroic layer formed on one surface of the ferromagnetic layer, wherein a surface of the multiferroic layer on the ferromagnetic layer side includes a first region, a crystalline phase of which is rhombohedral, and a second region, a crystalline phase of which is tetragonal.