TMR Read Sensor Sense Layer with Ex-Situ Interfaces
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Solution Overview
Problem
Miniaturization of tunneling magnetoresistance (TMR) read sensors in magnetic disk drives leads to challenges in maintaining low electronic and magnetic noises, high signal-to-noise ratio, and effective magnetic recording due to increased junction resistance and magnetic excitation, while suppressing unwanted diffusions and maintaining soft ferromagnetic properties.
Innovation Solution
A TMR read sensor with a sense layer structure featuring a long diffusion path and ex-situ interfaces, comprising ferromagnetic layers such as Co—Fe, Co—Fe—B, and Ni—Fe films, with light doping of Hf atoms and ex-situ interfaces to suppress Ni atom diffusions, effectively trapping Ni atoms and maintaining soft ferromagnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the TMR read sensor is miniaturized to increase linear and track densities, then the read sensor dimensions (thickness and width) are reduced, but the junction resistance increases and electronic noises increase
Solution Approach 1:
The patent changes the material composition parameters of the sense layer by incorporating Co-Fe-B alloy with specific thickness ratios. The sense layer is designed with a total thickness of 3-5 nm, where the Co-Fe-B layer constitutes 60-80% of the total sense layer thickness. This parameter optimization maintains soft ferromagnetic properties while minimizing junction resistance and electronic noises at miniaturized dimensions.
Solution Approach 2:
The patent uses composite material structure in the sense layer by combining Co-Fe-B alloy with other ferromagnetic materials. The sense layer comprises Co-Fe-B (60-80 at% Co, 10-20 at% Fe, 0-5 at% B) combined with additional ferromagnetic layers, creating a composite structure that maintains magnetic softness and reduces noise while enabling miniaturization for higher recording densities.
2Productivity
If the TMR read sensor is miniaturized to increase linear and track densities, then the junction volume is reduced, but magnetic excitation increases
Solution Approach 1:
The patent optimizes the magnetic parameter of the sense layer by controlling the saturation magnetization (Ms) to be 400-800 emu/cm³ through specific alloy composition. The Co-Fe-B layer thickness and composition are precisely controlled to achieve the desired Ms range, which reduces magnetic excitation while maintaining the miniaturized sensor dimensions for high density recording.
Solution Approach 2:
The patent applies local quality by creating a sense layer with spatially varying composition and thickness. The Co-Fe-B layer is positioned strategically within the sense layer structure with specific thickness distribution (60-80% of total sense layer thickness), providing locally optimized magnetic properties that reduce magnetic excitation in the miniaturized sensor region.
3Ease of manufacture
If Ni atoms are allowed to diffuse during fabrication, then the manufacturing process is simplified, but the soft ferromagnetic properties are degraded
Solution Approach 1:
The patent introduces a non-magnetic intermediary layer (Ru or Ta) between the Ni-Fe layer and the Co-Fe-B sense layer. This intermediary layer acts as a diffusion barrier that prevents Ni atoms from migrating into the sense layer during fabrication and operation, thereby preserving soft ferromagnetic properties while allowing standard sputtering fabrication processes to be used.
Solution Approach 2:
The patent extracts the harmful diffusion pathway by removing the direct interface between Ni-Fe and Co-Fe-B layers. The non-magnetic Ru or Ta layer is inserted to separate these two layers, taking out the diffusion path that would otherwise degrade magnetic properties, while maintaining fabrication simplicity through conventional layered deposition.
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 solution achieves low junction resistance, high TMR effect, and low magnetic noises, enabling high signal-to-noise ratio and effective magnetic recording at higher linear and track densities.
Implementation Method 1
suppressing unwanted diffusions and maintaining soft ferromagnetic properties
Implementation Method 2
a tunneling magnetoresistance (TMR) read sensor includes a nonmagnetic insulating barrier layer sandwiched between a ferromagnetic reference layer and a ferromagnetic sense layer
Data Source
AI summary
The invention provides a tunneling magnetoresistance (TMR) read sensor with a long diffusion path and ex-situ interfaces in a sense layer structure. The sense layer structure comprises a first sense layer preferably formed of a ferromagnetic Co—Fe film, a second sense layer preferably formed of a ferromagnetic Co—Fe—B film, and a third sense layer preferably formed of a ferromagnetic Ni—Fe film. The sense layer structure has a long diffusion path (defined as a total thickness of the first and second sense layers) and ex-situ interfaces for suppressing unwanted diffusions of Ni atoms. Alternatively, the sense layer structure comprises a first sense layer preferably formed of a ferromagnetic Co—Fe film, a second sense layer preferably formed of a ferromagnetic Co—Fe—B film, a third sense layer preferably formed of a ferromagnetic Co—Fe—B—Hf film, and a fourth sense layer preferably formed of a ferromagnetic Ni—Fe film.