Pinned Layer Setting in Magnetic Tunneling Junctions

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Solution Overview

Problem

Conventional spin transfer torque magnetic random access memories (STT-MRAMs) face difficulties in setting the magnetic moments of pinned layers in magnetic junctions effectively, which affects the efficiency of spin transfer and increases the offset field at the free layer.

Innovation Solution

A method and system are described for setting the magnetic moments of pinned layers in magnetic junctions by applying a magnetic field parallel to the easy axis of ferromagnetic layers, with a magnitude greater than the coercivity but less than the coupling field, and using a spin transfer current to switch the layers into a dual state, thereby improving spin transfer efficiency and reducing the offset field.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional methods are used to set pinned layers, then the magnetic moments can be set, but the spin transfer efficiency is reduced and offset field increases

Engineering Contradiction:

Improvesetting reliabilityVSAvoidspin transfer efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the magnetic field application parameters by applying a magnetic field parallel to the easy axis of the ferromagnetic layers with a magnitude greater than the coercivity but less than the coupling field. This parameter optimization enables reliable setting of magnetic moments while maintaining high spin transfer efficiency and reducing offset field at the free layer

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a magnetic field greater than coercivity is applied to set pinned layers, then magnetic moments are reliably set, but the offset field at the free layer increases

Engineering Contradiction:

Improvemagnetic moment settingVSAvoidoffset field

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes the magnetic field parameters by applying a field with magnitude greater than the coercivity but less than the coupling field, and by orienting the field parallel to the easy axis of the ferromagnetic layers. This controlled parameter change achieves reliable magnetic moment setting while minimizing the harmful offset field effect at the free layer

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If multiple magnetic layers are used in pinned layers, then magnetic stability is improved, but device complexity increases

Engineering Contradiction:

Improvemagnetic stabilityVSAvoidlayer structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent segments the pinned layer into multiple ferromagnetic layers with different coercivities, where each layer can be independently set by applying a magnetic field parallel to the easy axis. This segmentation provides magnetic stability through controlled layer configuration while simplifying the setting process compared to conventional approaches

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent utilizes parameter optimization by applying a magnetic field with specific magnitude (greater than coercivity but less than coupling field) and orientation (parallel to easy axis) to efficiently set the magnetic moments of the segmented ferromagnetic layers, achieving stable configuration without excessive complexity

Inventive Principle:

Principle #35Parameter changes

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 method allows for reliable setting of magnetic moments, enhancing spin transfer torque efficiency and reducing the offset field at the free layer, improving the performance of magnetic memories.

Implementation Method 1

A magnetic field is applied in a direction parallel to an easy axis of the ferromagnetic layers. The magnetic field has a magnitude greater than a coercivity of each of the layers and less than a coupling field between a portion of the layers.

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

The magnetic field has a magnitude greater than a coercivity of each of the layers

Methodology Applied

Scientific EffectCoercivity: Magnetic Hysteresis

Implementation Method 3

A spin polarized current driven through the magnetic junction exerts a spin torque on the magnetic moments in the magnetic junction. As a result, layer(s) having magnetic moments that are responsive to the spin torque may be switched to a desired state.

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS8697484B2Method and system for setting a pinned layer in a magnetic tunneling junction

Publication Date: 2014.04.15 SAMSUNG ELECTRONICS CO LTD

AI summary

A method and system for setting the direction of pinned layers in a magnetic junction are described. In one aspect, a magnetic field greater than the coercivity of the layers in a pinned layer but less than the coupling field between the layers is applied. In another aspect the pinned layers are switched from an anti-dual state to a dual state using a spin transfer torque current. In another aspect, a magnetic junction having a partial perpendicular anisotropy (PPMA) layer in the pinned layer is provided. In some aspects, the PPMA layer is part of a synthetic antiferromagnetic structure. In some embodiments, a decoupling layer is provided between the PPMA layer and another ferromagnetic layer in the pinned layer.