Active Magnetic Assist Layer for MRAM Switching

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Solution Overview

Problem

Current magnetic memory devices face limitations in efficiently switching the magnetization direction of free layers due to the passive nature of magnetic assist layers, which either help or hinder the switching process unpredictably, leading to inefficiencies in data storage and retrieval.

Innovation Solution

A three-terminal MRAM non-volatile memory cell design incorporating a spin Hall effect layer, a magnetic tunnel junction, and an active magnetic assist layer with a magnetization direction parallel to the plane, allowing for controlled oscillation and spin transfer torque to deterministically switch the free layer's magnetization direction by applying specific voltage pulses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a passive magnetic assist layer is used, then the device structure is simpler, but the switching of magnetization direction becomes unpredictable and inefficient

Engineering Contradiction:

Improvemagnetic assist layer structureVSAvoidswitching predictability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The magnetic assist layer is transformed from a static passive structure to a dynamic active structure that can oscillate its magnetization direction. By applying a first voltage pulse to the spin Hall effect layer, the magnetic assist layer's magnetization oscillates, enabling controlled interaction with the free layer to achieve deterministic switching.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements feedback control where the oscillation of the magnetic assist layer is modulated by voltage pulses applied to the spin Hall effect layer. This feedback mechanism allows precise control over when and how the magnetic assist layer interacts with the free layer, ensuring predictable switching behavior.

Inventive Principle:

Principle #23Feedback

2Ease of manufacture

If a passive magnetic assist layer is used, then the manufacturing process is simpler, but the switching efficiency deteriorates

Engineering Contradiction:

Improvemagnetic assist layer fabricationVSAvoidswitching efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The magnetic assist layer transitions from a static passive component to a dynamic active component capable of oscillation. This dynamic behavior, controlled by voltage pulses to the spin Hall effect layer, dramatically improves switching efficiency while maintaining compatibility with existing manufacturing processes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operational parameters of the magnetic assist layer by controlling its magnetization oscillation through voltage pulses. By modulating the amplitude and frequency of oscillation, the switching efficiency is optimized without requiring fundamental changes to the manufacturing process.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If voltage pulses are applied to induce oscillation, then deterministic switching is achieved, but energy consumption increases

Engineering Contradiction:

Improveswitching determinismVSAvoidvoltage pulse energy

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Instead of continuous energy application, the system uses periodic voltage pulses to induce oscillation in the magnetic assist layer. This periodic action allows the system to achieve deterministic switching while minimizing energy consumption by applying energy only during the pulse duration rather than continuously.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The dynamic oscillation of the magnetic assist layer creates a time-varying magnetic field that enhances the switching efficiency. This dynamic approach allows for lower energy pulses compared to static methods, as the oscillating magnetization provides stronger coupling with the free layer during critical switching moments.

Inventive Principle:

Principle #15Dynamics

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 design enhances the initial torque for switching and prevents undesired effects later in the process, improving the efficiency and reliability of data storage by ensuring deterministic switching of the free layer's magnetization direction, thus overcoming the limitations of passive magnetic assist layers.

Implementation Method 1

applying a first voltage pulse across the spin Hall effect layer to generate a spin orbit torque to cause the magnetization direction of the magnetic assist layer to oscillate

Methodology Applied

Scientific EffectSpin Hall Effect: Hall Effect

Implementation Method 2

a second voltage pulse across the magnetic tunnel junction and the magnetic assist layer to generate a spin transfer torque to cause the magnetization direction of the free layer to deterministically switch

Methodology Applied

Scientific EffectSpin Transfer Torque: Magnetism

Data Source

PatentUS11283008B1Apparatus and methods for magnetic memory devices with magnetic assist layer

Publication Date: 2022.03.22 SANDISK TECHNOLOGIES LLC

AI summary

An apparatus is provided that includes a magnetic tunnel junction, a magnetic assist layer coupled to the magnetic tunnel junction, a non-magnetic layer disposed between the free layer and the magnetic assist layer, and a spin Hall effect layer coupled to the magnetic assist layer. The magnetic tunnel junction includes a free layer in a plane, the free layer including a switchable magnetization direction perpendicular to the plane. The magnetic assist layer includes a magnetization direction parallel to the plane and free to rotate about an axis perpendicular to the plane.