Multi-Layer AFM Read Heads with Gradient Mn Composition

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Solution Overview

Problem

Magnetic recording hard disk read heads face challenges in maintaining a large exchange field and high thermal stability due to low Blocking Temperature Dispersion (TbD) in small Magnetic Tunnel Junction (MTJ) devices, which are exacerbated by non-uniform Mn composition in single-layer AFM films, leading to performance issues.

Innovation Solution

A multi-layer anti-ferromagnetic (AFM) layer with gradient Manganese (Mn) compositions is introduced, comprising multiple sub-layers with different Mn percentages, deposited using various gases like Argon (Ar) and Krypton (Kr), to enhance exchange field and thermal stability, with specific configurations achieving a large exchange field and strong Ruthenium (Ru) Synthetic Anti-ferromagnetic (SAF) performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single-layer AFM film is used, then the structure is simple, but the exchange field and thermal stability are insufficient

Engineering Contradiction:

ImproveAFM layer structureVSAvoidthermal stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single-layer AFM film is divided into multiple sub-layers with different Mn compositions. This segmentation allows each sub-layer to contribute differently to the overall exchange field and thermal stability, resolving the contradiction by making the structure more complex while significantly improving reliability through enhanced pinning strength and thermal stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses composite AFM layers with gradient Mn compositions (e.g., IrMn alloys with varying Mn percentages) to create a multi-layer structure. This composite approach combines materials with different properties to achieve both high exchange field and thermal stability, overcoming the limitations of single-layer homogeneous structures.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the Mn composition is non-uniform in single-layer AFM films, then manufacturing is easier, but the exchange field and pinning strength are reduced

Engineering Contradiction:

ImproveAFM film depositionVSAvoidpinning strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

Instead of uniform Mn composition, the patent implements local quality variations by creating sub-layers with different Mn concentrations. Each local region (sub-layer) has optimized composition for specific functions, with higher Mn content providing stronger exchange coupling and lower Mn content providing better thermal stability, thereby maintaining high pinning strength despite manufacturing variations.

Inventive Principle:

Principle #3Local quality

3Productivity

If the MTJ device size is reduced to increase track density, then productivity increases, but the blocking temperature dispersion decreases

Engineering Contradiction:

Improvetrack densityVSAvoidblocking temperature dispersion

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the compositional parameters of the AFM layer by introducing gradient Mn compositions in multiple sub-layers. This parameter optimization compensates for the reduced size effects in smaller MTJ devices, maintaining adequate blocking temperature dispersion and thermal stability even as device dimensions are reduced to increase track 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

The multi-layer AFM structure provides a large exchange field and high thermal stability, improving the performance of magnetic read heads by maintaining a strong pinning strength and orientation, overcoming the limitations of single-layer AFM films.

Implementation Method 1

a multi-layer anti-ferromagnetic (AFM) layer with gradient Manganese (Mn) compositions is introduced, comprising multiple sub-layers with different Mn percentages

Methodology Applied

Scientific EffectAnti-ferromagnetic coupling: Magnetism

Implementation Method 2

The pinned layer is usually held in a fixed magnetic orientation by its proximity to the exchange layer, which is a layer of antiferromagnetic material that fixes the pinned layer's magnetic orientation

Methodology Applied

Scientific EffectExchange coupling: Magnetism

Implementation Method 3

Different film compositions with a big range may be obtained from the same target by using Krypton (Kr) gas

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS10008219B2Recording read heads with a multi-layer AFM layer methods and apparatuses

Publication Date: 2018.06.26 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

Apparatuses and methods of recording read heads with a multi-layer anti-ferromagnetic (AFM) layer are provided. The AFM layer has gradient Manganese (Mn) compositions. A multi-layer AFM layer comprises a plurality of sub-layers having different Mn compositions. An upper sub-layer has a higher Mn composition than an lower sub-layer. Different types of gases may be used to deposit each sub-layer and the flow of each gas may be adjusted.