TMR Read Sensor Auxiliary Shield for Thermal Stability
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Solution Overview
Problem
Current magnetic disk drives with tunneling magnetoresistance (TMR) read sensors face challenges in achieving high-resolution magnetic recording due to limitations in miniaturization and thermal stability, particularly in maintaining low resistance-area product (RJAJ) and high tunnel magnetoresistance ratio (ΔRT/RJ) while ensuring effective shielding and thermal properties.
Innovation Solution
The integration of an auxiliary ferromagnetic shield comprising a buffer layer, parallel-coupling layer, shielding layer, and decoupling layer, formed of specific materials like Co—Hf, Ru, Ni—Fe, and Ir—Mn, enhances ferromagnetic continuity and permeability, leading to improved shielding and thermal stability, and is deposited at high temperatures to minimize surface roughness and optimize thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the TMR read sensor is miniaturized to increase linear and track densities, then storage capacity is improved, but thermal stability and shielding effectiveness deteriorate
Solution Approach 1:
The patent implements a nested multi-layer shield structure where the first ferromagnetic shield layer, second ferromagnetic shield layer, and auxiliary ferromagnetic shield are arranged concentrically around the TMR read sensor. Each layer is positioned at different distances from the sensor, creating a nested configuration that provides progressive shielding against thermal fluctuations and magnetic interference, thereby maintaining thermal stability in miniaturized sensors.
Solution Approach 2:
The patent employs composite material structures by combining multiple ferromagnetic shield layers with different material compositions and magnetic properties. The first and second ferromagnetic shield layers are made of different materials, and the auxiliary shield incorporates specific ferromagnetic materials, creating a composite shielding system that optimizes both thermal stability and magnetic shielding effectiveness in miniaturized TMR sensors.
2Productivity
If the read sensor dimensions are reduced to increase track density, then storage capacity is improved, but shielding effectiveness and signal quality worsen
Solution Approach 1:
The nested multi-layer shield structure surrounds the miniaturized TMR read sensor with progressively larger ferromagnetic shield layers at different radial distances. This nested configuration creates multiple zones of magnetic flux redirection, effectively shielding the small sensor from external magnetic interference and maintaining signal quality despite the reduced sensor dimensions.
Solution Approach 2:
The patent applies local quality by positioning the auxiliary ferromagnetic shield specifically at the lower edge of the TMR read sensor where magnetic interference is most critical. The shield layers are strategically placed at different distances from the sensor, with each layer providing localized shielding in specific regions, thereby maintaining signal quality in miniaturized sensors without requiring uniform shielding throughout the entire structure.
3Device complexity
If thinner shield layers are used to reduce device complexity, then manufacturing is simplified, but ferromagnetic continuity and permeability deteriorate
Solution Approach 1:
The patent uses composite material strategies by combining multiple thin ferromagnetic shield layers made of different materials with complementary magnetic properties. The first and second ferromagnetic shield layers are composed of different ferromagnetic materials, and the auxiliary shield adds another material layer, creating a composite structure where the combined magnetic properties achieve the required ferromagnetic continuity and permeability without requiring any single layer to be thick.
Solution Approach 2:
The patent merges multiple thin ferromagnetic shield layers into an integrated multi-layer shielding system. The first ferromagnetic shield layer, second ferromagnetic shield layer, and auxiliary ferromagnetic shield are combined in a coordinated configuration where each layer contributes to the overall ferromagnetic continuity. This merging of multiple thin layers achieves equivalent or superior magnetic properties compared to a single thick layer, while reducing device complexity.
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 results in a narrower read gap, higher permeability, and enhanced thermal stability, maintaining comparable TMR properties while increasing the tilting temperature (TT) by up to 46.2°C, ensuring high-resolution magnetic recording and operational reliability.
Implementation Method 1
The buffer layer, preferably formed of an amorphous ferromagnetic Co—X (where X is Hf, Y, Zr, etc.) film, creates microstructural discontinuity between a lower ferromagnetic shield and the TMR read sensor
Implementation Method 2
The parallel-coupling layer, preferably formed of a polycrystalline nonmagnetic Ru film, causes parallel coupling between the buffer and shielding layers
Implementation Method 3
The shielding layer, preferably formed of a polycrystalline ferromagnetic Ni—Fe film exactly identical to that used as the lower ferromagnetic shield, shields magnetic fluxes stemming from a recording medium into the lower edge of the TMR read sensor
Implementation Method 4
The decoupling layer, preferably formed of another polycrystalline nonmagnetic Ru film, causes decoupling between the shielding layer and a pinning layer preferably formed of a polycrystalline antiferromagnetic Ir—Mn film
Implementation Method 5
the buffer, parallel-coupling, shielding, decoupling and pinning layers are all deposited at high temperatures in one deposition module of a sputtering system
Implementation Method 6
When receiving a magnetic field emitting from data in the selected data track, the magnetization of the reference layer remains pinned while that of the sense layer rotates. Scattering decreases as the magnetization of the sense layer rotates towards that of the reference layer, or increases as the magnetization of the sense layer rotates away from that of the reference layer. This scattering variation induces a tunneling effect characterized by a change in the resistance of the CPP TMR read sensor
Data Source
AI summary
The invention provides a tunneling magnetoresistance (TMR) read sensor with an integrated auxiliary shield comprising buffer, parallel-coupling, shielding and decoupling layers for high-resolution magnetic recording. The buffer layer, preferably formed of an amorphous ferromagnetic Co—X (where X is Hf, Y, Zr, etc.) film, creates microstructural discontinuity between a lower ferromagnetic shield and the TMR read sensor. The parallel-coupling layer, preferably formed of a polycrystalline nonmagnetic Ru film, causes parallel coupling between the buffer and shielding layers. The shielding layer, preferably formed of a polycrystalline ferromagnetic Ni—Fe film exactly identical to that used as the lower ferromagnetic shield, shields magnetic fluxes stemming from a recording medium into the lower edge of the TMR read sensor. The decoupling layer, preferably formed of another polycrystalline nonmagnetic Ru film, causes decoupling between the shielding layer and a pinning layer preferably formed of a polycrystalline antiferromagnetic Ir—Mn film.