TMR Sensor Free-Layer Structure With Thin Nonmagnetic Interlayer

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Solution Overview

Problem

Existing tunneling magneto-resistive (TMR) sensors face challenges in achieving low coercivity (Hc) and high magnetic moment due to the crystalline structure influence from capping layers, which affects the sensitivity and performance of high-density magnetic recording applications.

Innovation Solution

Incorporating a non-magnetic layer, such as Ta or Hf, between the first and second free layers, and optionally an insertion layer to break the crystalline structure translation, combined with a capping layer modification, results in a magnetically softer and more amorphous free layer structure with reduced Hc and increased magnetic moment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional free layer structure with capping layer is used, then the crystalline structure is maintained, but the coercivity (Hc) increases and magnetic moment decreases

Engineering Contradiction:

Improvemagnetic momentVSAvoidcoercivity (Hc)

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A nonmagnetic material layer (such as Ru, Rh, Ir, Pt, Pd, Ag, Au, Cu, Al, Si, or their alloys) is inserted between the capping layer and the free layer. This intermediary layer breaks the crystalline structure translation from the capping layer to the free layer, making the free layer more amorphous, thereby reducing coercivity while maintaining or enhancing magnetic moment

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the structural parameter by introducing a nonmagnetic insertion layer with specific thickness (e.g., 1-10 Å) and material composition. This parameter change disrupts the crystalline ordering and modifies the magnetic properties of the free layer, achieving lower Hc and higher magnetic moment

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the capping layer crystalline structure is directly transferred to the free layer, then the structure is simplified, but the TMR sensor sensitivity decreases

Engineering Contradiction:

ImproveTMR sensor sensitivityVSAvoidfree layer structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The nonmagnetic material layer serves as a mediator that decouples the crystalline structure relationship between the capping layer and free layer. This allows the free layer to maintain a more amorphous structure with better magnetic properties while still being part of the overall layered structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The free layer structure is segmented into multiple sub-layers with different functions: the free layer itself, the nonmagnetic insertion layer, and the capping layer. This segmentation allows each layer to be optimized independently for its specific function

Inventive Principle:

Principle #1Segmentation

3Object-affected harmful factors

If a thin nonmagnetic layer is inserted between free layers, then the free layer becomes more amorphous with lower Hc, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvecoercivity (Hc)VSAvoidnonmagnetic layer thickness control

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent specifies a thin thickness range (1-10 Å) for the nonmagnetic layer to achieve the desired amorphous structure and magnetic property improvement while minimizing the impact on manufacturing precision requirements

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 free layer structure achieves low Hc, high magnetic moment, and high MR ratio, enhancing the sensitivity and performance of TMR sensors for next-generation magnetic recording applications.

Implementation Method 1

Inserting the non-magnetic layer can break the translation of the first free layer crystalline structure to the second free layer, thus making the second free layer more amorphous

Methodology Applied

Scientific EffectCrystalline structure disruption:

Implementation Method 2

tunneling magneto-resistive (TMR) sensor... an electrical resistance of the TMR sensor can decrease when magnetization directions of the pin layer and free layer are in parallel, and the electrical resistance of the TMR sensor can increase when magnetization directions of the pin layer and free layer are anti-parallel

Methodology Applied

Scientific EffectTunneling magneto-resistive effect: Magnetoresistance

Data Source

PatentUS20250295039A1Tunnel Magneto-Resistive Sensor With Thin Nonmagnetic Material In Free Layer

Publication Date: 2025.09.18 HEADWAY TECHNOLOGIES INC

AI summary

The present embodiments relate to a free layer structure of a sensor (e.g., a tunneling magneto-resistive (TMR) sensor) with a non-magnetic layer deposited between free layers. For instance, a free layer structure can be created by inserting a subatomic non-magnetic layer with materials such as Tantalum (Ta) or Hafnium (Hf) between a first free layer and a second free layer. Inserting the non-magnetic layer can break the translation of the first free layer crystalline structure to the second free layer, thus making the second free layer more amorphous. The free layer structure can also include inserting an insertion layer before depositing a capping layer, which can reduce the influence of the capping layer crystalline structure to the free layer. Another example free layer structure can include inserting both the non-magnetic layer and the insertion layer to obtain a magnetically softer film.