SOT-MRAM Voltage Control for Stable Magnetization Inversion

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Solution Overview

Problem

In SOT-MRAMs, achieving stable magnetization inversion with perpendicular magnetization films is challenging due to varying current and pulse width requirements across integrated magnetic memory elements, which leads to inversion errors, especially under temperature variations.

Innovation Solution

A magnetic memory with a laminated structure including a magnetic layer, an insulating layer, and a voltage application layer that applies voltage simultaneously with current flow to change magnetic anisotropy or damping constants, allowing for stable magnetization inversion by controlling voltage and current patterns across multiple memory elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a perpendicular magnetization film is used in SOT-MRAM, then the recording capacity is improved, but the magnetization inversion stability deteriorates due to varying current and pulse width requirements

Engineering Contradiction:

Improverecording capacityVSAvoidmagnetization inversion stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies voltage to the magnetic layer to dynamically change magnetic anisotropy and damping constants, thereby adjusting the magnetization inversion characteristics. This parameter change approach allows the system to adapt to variations in current and pulse width requirements across different magnetic memory elements, improving inversion stability while maintaining high recording capacity with perpendicular magnetization films

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic control by applying voltage during the magnetization inversion process. The voltage application layer actively modulates the magnetic anisotropy and damping constants in real-time, transforming the static magnetic properties into dynamically adjustable parameters. This enables stable inversion across multiple memory elements despite variations in operating conditions

Inventive Principle:

Principle #15Dynamics

2Reliability

If strict control of current value and pulse width is implemented, then the magnetization inversion stability is improved, but the device complexity increases

Engineering Contradiction:

Improvemagnetization inversion stabilityVSAvoidcontrol mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of strictly controlling current value and pulse width, the patent changes the magnetic properties (anisotropy and damping constants) through voltage application. This parameter change approach simplifies the control mechanism by adjusting the magnetic layer's intrinsic properties rather than precisely controlling external electrical parameters, thereby improving inversion stability without significantly increasing device complexity

Inventive Principle:

Principle #35Parameter changes

3Reliability

If voltage is applied to change magnetic anisotropy and damping constants, then the inversion error is suppressed, but the energy consumption increases

Engineering Contradiction:

Improveinversion accuracyVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies voltage periodically or in pulses synchronized with the magnetization inversion process. By applying voltage only when needed (during or near the inversion timing) rather than continuously, the energy consumption is minimized while still achieving the desired suppression of inversion errors through dynamic modulation of magnetic anisotropy and damping constants

Inventive Principle:

Principle #19Periodic action

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 approach enables stable recording while suppressing inversion errors by optimizing magnetic anisotropy and damping constants, ensuring reliable magnetization direction changes across multiple memory elements.

Implementation Method 1

a spin orbit layer that provides spin orbit torque to the magnetic layer

Methodology Applied

Scientific EffectSpin orbit torque:

Implementation Method 2

spin polarization induced when a current flows in a nonmagnetic metal

Methodology Applied

Scientific EffectSpin polarization:

Implementation Method 3

applies a voltage to the magnetic layer at a same time as the current flowing in the spin orbit layer to change magnetic anisotropy or a magnetic damping constant of the magnetic layer

Methodology Applied

Scientific EffectMagnetic anisotropy change:

Implementation Method 4

applies a voltage to the magnetic layer at a same time as the current flowing in the spin orbit layer to change magnetic anisotropy or a magnetic damping constant of the magnetic layer

Methodology Applied

Scientific EffectMagnetic damping constant change:

Data Source

PatentUS11069389B2Magnetic memory and magnetic memory recording method

Publication Date: 2021.07.20 SONY SEMICON SOLUTIONS CORP

AI summary

To provide a magnetic memory capable of performing stable recording while suppressing occurrence of an inversion error. Provided is a magnetic memory including a spin orbit layer in which a spin-polarized electron is generated by a current, a magnetic memory element having a laminated structure including a magnetic layer in which a magnetization direction changes according to information to be recorded and an insulating layer, and provided on the spin orbit layer, and a voltage application layer for applying a voltage to the magnetic layer via the insulating layer, in which the voltage application layer applies a voltage to the magnetic layer at a same time as the current flowing in the spin orbit layer to change magnetic anisotropy or a magnetic damping constant of the magnetic layer.