Multiferroic Memory Voltage-Controlled Strain Switching

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Solution Overview

Problem

Current magnetoresistive random access memory (MRAM) devices face limitations in write current and resultant heat generation, which constrain memory densities and efficiency.

Innovation Solution

The development of an electronic device with a multiferroic tunnel junction (MFTJ) architecture, utilizing piezoelectric and magnetostrictive layers to switch the ferromagnetic layer via voltage-controlled strain, enabling low-power, high-density storage with eight distinct logic/memory states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If current-driven write operation is used in MRAM, then magnetization switching can be achieved, but heat generation increases and write current is limited

Engineering Contradiction:

Improvewrite currentVSAvoidheat generation

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent replaces the electrical current-driven write operation with a voltage-driven piezoelectric actuation mechanism. The piezoelectric layer converts voltage into mechanical strain, which acts on the magnetostrictive layer to switch magnetization without requiring high write currents, thereby reducing heat generation and power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the control parameter for write operation from current (in conventional MRAM) to voltage (in the piezoelectric-driven MFTJ). This parameter change enables magnetization switching through voltage-controlled strain rather than current-driven spin transfer torque, fundamentally reducing the energy required for write operations.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If higher memory density is achieved, then storage capacity increases, but heat dissipation limits are reached

Engineering Contradiction:

Improvememory densityVSAvoidheat dissipation

Core Design Contradiction:

Quantity of substanceVSTemperature

Solution Approach 1:

By replacing current-driven magnetization switching with voltage-driven piezoelectric actuation, the patent enables higher memory density integration without proportionally increasing heat generation. The voltage-driven mechanism consumes significantly less power, allowing more memory cells to be packed into the same area without exceeding thermal limits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by moving object

If piezoelectric and magnetostrictive layers are integrated, then power consumption is reduced, but device structure becomes more complex

Engineering Contradiction:

Improvepower consumptionVSAvoiddevice structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent merges the piezoelectric layer and magnetostrictive layer into a single integrated stack structure. The piezoelectric layer is positioned adjacent to the magnetostrictive layer, allowing direct mechanical coupling. This integration enables the piezoelectric actuation to directly influence the magnetostrictive layer's magnetization state, achieving low-power operation while maintaining a compact, unified device architecture.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs a composite structure combining piezoelectric material and magnetostrictive material in close proximity. The piezoelectric material (e.g., Pb(Zr,Ti)O3 or Pb1-xLaxZr1-yTiyO3) and magnetostrictive material (e.g., Terfenol-D or similar) work together to achieve voltage-controlled magnetization switching, creating a multifunctional composite device that reduces power consumption.

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 approach achieves reduced power requirements and improved storage densities, enabling efficient low-power operation and high-bandwidth memory, particularly beneficial for artificial intelligence and machine learning applications.

Implementation Method 1

The first piezoelectric layer may be strained responsive to voltage applied across the first and second electrodes

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a first magnetostrictive layer above the first piezoelectric layer

Methodology Applied

Scientific EffectMagnetostriction: Magnetostriction

Data Source

PatentUS12274073B2Multiferroic memory with piezoelectric layers and related methods

Publication Date: 2025.04.08 EAGLE TECHNOLOGY LLC

AI summary

An electronic device may include a first electrode, a first piezoelectric layer electrically coupled to the first electrode, a first magnetostrictive layer above the first piezoelectric layer, a first tunnel barrier layer above the first magnetostrictive layer, and a ferromagnetic layer above the first ferroelectric layer. The electronic device may further include a second electrode electrically coupled to the ferromagnetic layer a second tunnel barrier layer above the ferromagnetic layer, a second magnetostrictive layer above the second tunnel barrier layer, a second piezoelectric layer above the second magnetostrictive layer, and a third electrode electrically coupled to the second piezoelectric layer. The first piezoelectric layer may be strained responsive to voltage applied across the first and second electrodes, and the second piezoelectric layer may be strained responsive to voltage applied across the second and third electrodes.