Recessed BiSb Layer in SOT Magnetic Recording Head

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Solution Overview

Problem

BiSb materials used in spin-orbit torque (SOT) devices face challenges such as low melting points, large grain sizes, significant Sb migration issues, difficulty in maintaining desired crystal orientations, and susceptibility to damage during processing.

Innovation Solution

A magnetic recording head design incorporating a SOT device with a recessed BiSb layer, where the BiSb layer is disposed over a free layer and recessed from the media facing surface (MFS), and shield notches are used to further recess the BiSb layer and reduce shield-to-shield spacing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If BiSb layer is exposed at the media facing surface (MFS), then the spin Hall effect performance is maximized, but the device is prone to damage by oxidation and thermal-mechanic stresses

Engineering Contradiction:

Improvestability and durability of BiSb layerVSAvoidoxidation and thermal-mechanic stresses

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The BiSb layer is extracted from the media-facing surface and recessed into the structure, removing it from direct exposure to harmful environmental factors while preserving its functional properties through strategic positioning deeper within the device architecture

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The solution transitions from a two-dimensional surface exposure configuration to a three-dimensional recessed configuration, moving the BiSb layer away from the MFS along the vertical dimension to eliminate direct contact with oxidation and thermal-mechanic stresses

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If BiSb layer is recessed from the media facing surface (MFS), then the stability and durability are improved, but the signal-to-noise ratio may be reduced

Engineering Contradiction:

Improvestability and durability of BiSb layerVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The device structure is designed with localized optimization where the BiSb layer is recessed to specific depths and positions that balance protection needs with signal detection requirements, creating different functional zones within the device structure

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The design replaces direct surface exposure with a shielded configuration, using structural arrangement and material positioning to substitute the mechanical protection function while maintaining the electromagnetic signal detection capability through optimized geometry

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If shield notches are used to recess the BiSb layer, then the shield-to-shield spacing is reduced, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveshield-to-shield spacingVSAvoidrecess depth and orientation control

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The shield notches are designed and positioned in advance during the fabrication process, pre-establishing the recessed configuration of the BiSb layer before final assembly, which allows for controlled manufacturing of the notch geometry and positioning

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The shield structure is segmented with notches that create discrete recessed regions, allowing the BiSb layer to be positioned in specific zones where the notch geometry controls the recess depth and orientation, breaking down the continuous shield into functional segments

Inventive Principle:

Principle #1Segmentation

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 signal-to-noise ratio and improves the stability and durability of the BiSb layer, reducing the risk of damage and oxidation, while maintaining optimal crystal orientation for enhanced spin Hall effect performance.

Implementation Method 1

BiSb layers are narrow band gap topological insulators with both giant spin Hall effect and high electrical conductivity

Methodology Applied

Scientific EffectSpin Hall Effect: Hall Effect

Implementation Method 2

the HDD reader device is even more prone to being damaged by oxidation or more thermal-mechanic stresses

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS12334123B2Spin-orbit torque SOT reader with recessed spin hall effect layer

Publication Date: 2025.06.17 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

The present disclosure generally relates to a magnetic recording head comprising one or more spin-orbit torque (SOT) devices, the SOT devices each comprising a bismuth antimony (BiSb) layer. The magnetic recording head comprises a SOT device comprising a first shield extending to a media facing surface (MFS), a seed layer disposed over the first shield, the seed layer being disposed at the MFS, a free layer disposed on the seed layer, the free layer being disposed at the MFS, a bismuth antimony (BiSb) layer disposed over the free layer, the BiSb layer being recessed from the MFS, a second shield disposed over the BiSb layer, the second shield extending to the MFS, and a shield notch coupled to the second shield, the shield notch being disposed between the first shield and the second shield. The magnetic recording head may be a two-dimensional magnetic recording head comprising two SOT devices.