Magnetic Sensor Doped Ferromagnetic Cap Underlayer Read Gap

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Solution Overview

Problem

The miniaturization of magnetic sensor components in hard disk drives (HDDs) faces challenges in reducing the read gap between magnetic shields while maintaining signal stability and magnetic recording density, as conventional magnetic materials destabilize the sensor stack under spin torque.

Innovation Solution

Incorporating a soft ferromagnetic material doped with high spin orbit coupling materials like Dy, Tb, Ir, Pt, Pd, Os, Ho, Gd, Er, W, and Rh in the cap and underlayer of magnetic heads, which reduces the read gap and improves signal stability by increasing spin-flip scattering and decoupling spin-polarized electric currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the spacing between magnetic shields (read gap) is reduced to improve resolution and recording density, then measurement precision and productivity are improved, but the sensor signal stability deteriorates due to spin torque destabilization from conventional magnetic materials

Engineering Contradiction:

ImproveresolutionVSAvoidsensor signal stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The invention changes the magnetic material parameters by doping soft ferromagnetic materials with high spin-orbit coupling materials (Ir, Pt, Pd, Os, Rh, W, Re) at specific concentrations (0.1-10 at%). This modifies the spin torque characteristics and increases spin-flip scattering, allowing reduced read gap while maintaining signal stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses composite magnetic materials combining soft ferromagnetic materials with high spin-orbit coupling materials. This composite structure provides both the magnetic properties needed for shield function and the spin-orbit coupling effects needed to stabilize sensor signals at reduced read gaps

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If conventional magnetic materials are used in the cap and underlayer, then ease of manufacture is maintained, but the sensor stack becomes destabilized under spin torque

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidsensor stack stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention modifies the composition parameters of conventional soft ferromagnetic materials by adding small amounts (0.1-10 at%) of high spin-orbit coupling materials. This maintains manufacturing compatibility with existing processes while fundamentally changing the spin torque behavior to prevent destabilization

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the read gap is reduced to increase recording density, then productivity is improved, but manufacturing precision becomes more difficult due to thickness limits of individual sensor layers

Engineering Contradiction:

Improverecording densityVSAvoidlayer thickness control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention changes the magnetic material composition to include high spin-orbit coupling materials, which alter the spin torque characteristics. This allows the use of thinner nonmagnetic spacer layers without compromising signal stability, enabling reduced read gap and increased recording density

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

This configuration enhances the functionality and accuracy of magnetic heads by reducing the read gap and preventing destabilization of the sensor stack, thereby improving recording density and signal-to-noise ratio.

Implementation Method 1

Methodology Applied

Scientific EffectSpin-orbit coupling:

Data Source

PatentUS9099115B2Magnetic sensor with doped ferromagnetic cap and/or underlayer

Publication Date: 2015.08.04 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A magnetic head according to one embodiment includes an underlayer, a first nonmagnetic spacer layer above the underlayer, a free layer above the first nonmagnetic spacer layer, a second nonmagnetic spacer layer above the free layer, and a cap layer above the second nonmagnetic spacer layer. At least one of the cap layer and the underlayer comprises a soft ferromagnetic material and a high spin orbit coupling material. Other embodiments are also described.