Orthogonal Spin Transfer MRAM with Perpendicular Magnetization

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Solution Overview

Problem

Orthogonal spin transfer magnetic random access memory devices face challenges in maintaining long-term stability of magnetic states and reducing write error rates for sub-nanosecond write pulses, especially in densely packed memory arrays, where interaction between magnetic devices is significant.

Innovation Solution

The implementation of a magnetic device with a pinned polarizing layer, a free layer with perpendicular magnetization, and a reference layer, separated by non-magnetic layers, allows for balanced switching currents and stable magnetic states, enabling efficient data storage with reduced write error rates and simplified circuitry, using synthetic antiferromagnet layers to optimize magnetic interactions and balance switching currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If orthogonal spin transfer magnetic random access memory devices are used for fast write operations, then write speed is improved, but write error rate increases for sub-nanosecond pulses

Engineering Contradiction:

Improvewrite speedVSAvoidwrite error rate

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent changes the magnetization orientation parameter from in-plane to perpendicular magnetization in the free layer, and uses synthetic antiferromagnet layers to control magnetic coupling parameters. This enables balanced switching currents that reduce write error rates while maintaining fast sub-nanosecond write speeds through optimized spin transfer torque mechanisms

Inventive Principle:

Principle #35Parameter changes

2Productivity

If magnetic devices are densely packed to increase storage density, then productivity is improved, but interaction between magnetic devices increases causing instability

Engineering Contradiction:

Improvestorage densityVSAvoidmagnetic state stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent introduces non-magnetic intermediary layers between adjacent magnetic devices to isolate magnetic interactions. These spacer layers prevent cross-talk and magnetic interference between densely packed devices, enabling high storage density while maintaining individual device stability through magnetic field isolation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If conventional magnetic memory structures are used, then device complexity is reduced, but long-term stability of magnetic states deteriorates

Engineering Contradiction:

Improvestructure complexityVSAvoidmagnetic state stability

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent employs composite magnetic structures including synthetic antiferromagnet layers composed of multiple thin magnetic and non-magnetic layers. This composite architecture provides enhanced magnetic state stability through controlled exchange coupling and anisotropy, achieving long-term data retention while maintaining fabrication compatibility with conventional processes

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 configuration achieves long-term stability of magnetic states, reduced write error rates, and simplified circuitry, allowing for efficient data storage in densely packed memory arrays with scalable device size, while maintaining fast write processes.

Implementation Method 1

This assures that a spin-transfer torque acts on a switchable magnetic layer (free layer) of the device when a write pulse (a voltage or current pulse) is applied to a device

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 2

The magnetic device also includes a free layer, separated from the polarizing magnetic layer by a first non-magnetic layer

Methodology Applied

Scientific EffectMagnetic separation:

Data Source

PatentUS9773837B2Scalable orthogonal spin transfer magnetic random access memory devices with reduced write error rates

Publication Date: 2017.09.26 NEW YORK UNIV

AI summary

A magnetic device includes a pinned polarizing magnetic layer having a magnetic vector parallel to a plane of the pinned polarizing magnetic layer. The magnetic device also includes a free layer, separated from the polarizing magnetic layer by a first non-magnetic layer, having a magnetization vector with a changeable magnetization direction. The changeable magnetization vector is configured to change to a first state upon application of a first current of a first polarity and to change to a second state upon application of a second current of a second, opposite polarity. The magnetic device also has a reference layer having a magnetic vector perpendicular to the plane of the reference layer and separated from the free layer by a second non-magnetic layer.