CPP Read Sensor with Ferromagnetic Buffer and Shielding Layers
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Solution Overview
Problem
Current CPP TMR and GMR read sensors in magnetic disk drives face limitations in achieving higher linear and track densities due to constraints in the thickness and width of their components, necessitating further miniaturization while maintaining magnetic and TMR properties.
Innovation Solution
Incorporation of ferromagnetic buffer, shielding, and seed layers, specifically amorphous Co—X films for buffers, polycrystalline Ni—Fe films for shielding, and polycrystalline Ni—X films with a face-centered-cubic structure for seeds, to facilitate preferred crystalline textures and magnetic continuity, reducing the read gap and enhancing magnetic and TMR properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the read sensor components is reduced to increase linear density, then linear density increases, but magnetic properties and TMR properties deteriorate
Solution Approach 1:
The patent changes the material composition and structural parameters of the buffer and seed layers. Specifically, it uses amorphous Co-X alloys for buffer layers and polycrystalline Ni-X alloys with face-centered-cubic structure for seed layers, optimizing their thickness and composition to maintain magnetic properties while enabling read sensor miniaturization.
Solution Approach 2:
The patent employs composite material structures by combining amorphous Co-X buffer layers with polycrystalline Ni-X seed layers, and further integrating them with the read sensor stack. This composite approach allows each layer to contribute specific properties: the amorphous buffer provides magnetic continuity and structural stability, while the polycrystalline seed layer promotes preferred crystalline textures, together maintaining TMR properties at reduced dimensions.
2Quantity of substance
If the width of the read sensor components is reduced to increase track density, then track density increases, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The patent optimizes the thickness parameters of the buffer and seed layers to control the growth and dimensions of the read sensor. By carefully selecting layer thicknesses and material compositions, the patent enables precise control over the final read sensor width, facilitating higher track density while maintaining manufacturing precision.
3Measurement precision
If the read gap is reduced to increase resolution, then linear and track densities increase, but thermal stability and coercivity may be compromised
Solution Approach 1:
The patent uses a composite structure of amorphous Co-X buffer layers and polycrystalline Ni-X seed layers to achieve the reduced read gap while maintaining thermal stability. The amorphous nature of the buffer layer provides magnetic continuity without grain boundary effects, and the polycrystalline seed layer promotes desired crystalline textures, together enabling a 4 nm read gap reduction while preserving coercivity and thermal stability.
Solution Approach 2:
The patent changes the material parameters of the buffer and seed layers to compensate for the reduced read gap. By optimizing the composition and thickness of these layers, the patent maintains the necessary magnetic anisotropy and coercivity values even with the smaller read gap, ensuring thermal stability is not compromised.
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 use of these layers allows for a reduction in the read gap by 4 nm without deteriorating magnetic and TMR properties, ensuring robust thermal stability and maintaining high coercivity and anisotropy values, thus enabling increased linear and track densities in magnetic recording.
Implementation Method 1
The ferromagnetic buffer layer is preferably formed of an amorphous Co—X (where X is Hf, Y, Zr, etc.) film. It provides the CPP read sensor with microstructural discontinuity from a ferromagnetic lower shield, thus facilitating the CPP read sensor to grow freely with preferred crystalline textures, but with ferromagnetic continuity to the ferromagnetic lower shield
Implementation Method 2
The ferromagnetic shielding layer is preferably formed of a polycrystalline Ni—Fe film. It exhibits magnetic properties exactly identical to those of the ferromagnetic lower shield, thus acting identically as the ferromagnetic lower shield. It also exhibits a uniform columnar grain morphology distinctly different from a non-uniform equal-axial grain morphology in the ferromagnetic lower shield
Implementation Method 3
The ferromagnetic seed layer is preferably formed of a polycrystalline Ni—X (where X is Pt, Pd, Rh, Ru, etc.) film that exhibits a face-centered-cubic (fcc) structure and does not exchange-couple with the antiferromagnetic pinning layer. It provides the CPP read sensor with microstructural continuity, thus facilitating the CPP read sensor to develop preferred crystalline textures and exhibit good magnetic and TMR properties
Implementation Method 4
A current-perpendicular-to-plane (CPP) tunneling magnetoresistance (TMR) or giant magnetoresistance (GMR) read sensor is typically used in the read head
Implementation Method 5
A current-perpendicular-to-plane (CPP) tunneling magnetoresistance (TMR) or giant magnetoresistance (GMR) read sensor is typically used in the read head
Data Source
AI summary
A current-perpendicular-to-plane (CPP) tunneling magnetoresistance (TMR) or giant magnetoresistance (GMR) read sensor with ferromagnetic buffer, shielding and seed layers is proposed for high-resolution magnetic recording. The ferromagnetic buffer layer is preferably formed of an amorphous Co—X (where X is Hf, Y, Zr, etc.) film. It provides the CPP read sensor with microstructural discontinuity from a ferromagnetic lower shield, thus facilitating the CPP read sensor to grow freely with preferred crystalline textures, and with ferromagnetic continuity to the ferromagnetic lower shield, thus acting as a portion of the ferromagnetic lower shield. The ferromagnetic shielding layer is preferably formed of a polycrystalline Ni—Fe film. It exhibits magnetic properties exactly identical to those of the ferromagnetic lower shield, thus acting identically as the ferromagnetic lower shield, and a uniform columnar grain morphology, thus initiating a uniform large grain morphology in the CPP read sensor.