TDMR Read Head Shield Layout for Correct Side-Shield Magnetization

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Solution Overview

Problem

The magnetization direction of the SB side shields in two dimensional magnetic recording (TDMR) read heads can be incorrectly affected by the SAF layer between the sets of SB side shields, leading to improper operation.

Innovation Solution

The TDMR read head is designed with specific shield configurations, including a middle shield comprising a ferromagnetic (FM) layer, antiferromagnetic (AFM) layer, and additional FM layers, and an upper shield as a synthetic antiferromagnetic (SAF) pinned shield or simple pinned shield, to align the magnetization directions correctly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a SAF layer is disposed between the two sets of SB side shields, then the read head structure is completed, but the magnetization direction of the SB side shields may be incorrectly affected leading to improper operation

Engineering Contradiction:

Improveproper operation of read headVSAvoidshield configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A non-magnetic layer is introduced as an intermediary between the SAF layer and the SB side shields. This intermediary layer prevents direct magnetic interaction between the SAF layer and the SB side shields, thereby eliminating the harmful magnetic field effect that causes incorrect magnetization direction while maintaining the structural integrity of the read head

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful magnetic interaction is extracted or isolated by placing a non-magnetic barrier layer between the SAF layer and the SB side shields. This separates the magnetic components that were directly interacting, preventing the unwanted magnetic field influence on the SB side shields magnetization direction

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If the magnetization direction of SB side shields is incorrect, then the read head structure remains complete, but the read head ceases to operate as intended

Engineering Contradiction:

Improveoperational reliabilityVSAvoidincorrect magnetization direction

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A non-magnetic layer is positioned between the SAF layer and the SB side shields to act as a magnetic field barrier. This intermediary prevents the SAF layer's magnetic field from incorrectly affecting the magnetization direction of the SB side shields, ensuring they maintain the correct magnetization orientation for proper read head operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The non-magnetic layer is placed in advance between the SAF layer and SB side shields to preemptively block the harmful magnetic field interaction before it can occur. This preliminary protective measure ensures the SB side shields are never exposed to the incorrect magnetic field that would cause operational failure

Inventive Principle:

Principle #9Preliminary anti-action

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 ensures proper operation of the TDMR read head by aligning the SB side shields correctly, improving performance and reducing signal-to-noise ratio.

Implementation Method 1

a first sensor, oftentimes referred to as a lower reader and a second sensor, oftentimes referred to as an upper reader. The readers each have lower and upper shields with a middle shield therebetween. Both the top reader and the bottom reader are substantially identical, each comprising either a single free layer (SFL) or two free layers to be dual free layer (DFL) readers or sensors. In DFL reader operation, the two free layers of each reader are individually stabilized longitudinally by an anti-ferromagnetically coupled (AFC) soft bias (SB) side shields

Methodology Applied

Scientific EffectExchange coupling: Magnetism

Implementation Method 2

DFL TDMR read heads generally comprise two sets of SB side shields disposed on either side of the two free layers with a synthetic antiferromagnetic (SAF) layer disposed therebetween. The magnetization direction of the two SB side shields should be anti-parallel.

Methodology Applied

Scientific EffectAntiferromagnetic coupling: Magnetism

Implementation Method 3

biased transversally by a permanent magnet or a rear hard bias (RHB) structure from the stripe back edge of the sensor

Methodology Applied

Scientific EffectMagnetic bias: Magnetism

Data Source

PatentUS20250391427A1Shield Designs for Two Dimensional Magnetic Recording Read Heads

Publication Date: 2025.12.25 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

The present disclosure generally relates to a two dimensional magnetic recording (TDMR) read head. The read head comprises a lower shield, a lower sensor disposed on the lower shield, a middle shield disposed over the lower sensor, an upper sensor disposed on the middle shield, and an upper shield disposed over the upper sensor. In one embodiment, the middle shield is a simple pinned shield comprising a first ferromagnetic (FM) layer, an antiferromagnetic (AFM) layer disposed on the first FM layer, and a second FM layer disposed on the AFM layer, and the upper shield is a synthetic antiferromagnetic (SAF) pinned shield comprising a first pinning layer, an antiferromagnetic coupling (AFC) layer disposed on the first pinning layer, and a second pinning layer disposed on the AFC layer. In another embodiment, the middle shield is a SAF pinned shield and the upper shield is a simple pinned shield.