Tunneling Magnetic Sensing Element Gradient Fe Enhancing Layer
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Solution Overview
Problem
Existing tunneling magnetic sensing elements face challenges in achieving a high rate of change in resistance (ΔR/R) while maintaining low magnetostriction of the free magnetic layer, leading to unsatisfactory detection sensitivity and stability in magnetic playback heads.
Innovation Solution
A tunneling magnetic sensing element is designed with a laminated structure where the enhancing layer has a higher Fe content on the side interfacing with the barrier layer and a lower Fe content on the side interfacing with the soft magnetic layer, forming a gradient to minimize magnetostriction and maximize resistance change, using a CoFe alloy and specific Fe content ratios for the enhancing layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Fe content in the enhancing layer is increased to improve the rate of change in resistance (ΔR/R), then the magnetostriction value λ of the free magnetic layer increases, which deteriorates the stability of the magnetic playback head
Solution Approach 1:
The enhancing layer is designed with non-uniform Fe content distribution, having higher Fe content on the barrier layer side and lower Fe content on the soft magnetic layer side. This local quality variation allows the region near the barrier layer to provide high spin polarizability for increased ΔR/R, while the region near the soft magnetic layer maintains low magnetostriction for stability.
Solution Approach 2:
The enhancing layer is divided into multiple sub-layers with different Fe content ratios. This segmentation enables different portions of the enhancing layer to fulfill different functions: the high-Fe-content portion maximizes resistance change, while the low-Fe-content portion minimizes magnetostriction-induced instability.
2Measurement precision
If a uniform high Fe content is used throughout the enhancing layer to maximize spin polarizability and ΔR/R, then the magnetostriction increases significantly, counteracting the benefits of high spin polarizability
Solution Approach 1:
Instead of uniform composition, the enhancing layer employs a gradient Fe content distribution that varies spatially. The high Fe content region (near barrier layer) optimizes spin polarizability for detection sensitivity, while the low Fe content region (near soft magnetic layer) suppresses magnetostriction for magnetic stability.
Solution Approach 2:
The enhancing layer functions as a composite structure with multiple CoFe alloy layers having different compositions. This composite approach combines the advantages of high-Fe-content materials (high spin polarizability) with low-Fe-content materials (low magnetostriction) within a single functional layer.
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 effectively increases the rate of change in resistance (ΔR/R) while keeping magnetostriction low, enhancing detection sensitivity and stability of the magnetic playback head.
Implementation Method 1
the resistance is improved by the use of a tunnel effect. When the magnetization of a pinned magnetic layer and the magnetization of a free magnetic layer are antiparallel to each other, it is difficult for a tunnel current to pass through a tunnel barrier layer
Data Source
AI summary
A tunneling magnetic sensing element is provided, in which an increase in the magnetostriction of a free magnetic layer is reduced and the rate of change in resistance is high. A laminate T1 constituting the tunneling magnetic sensing element includes a portion in which a pinned magnetic layer, a barrier layer, and a free magnetic layer are disposed in that order from the bottom. An enhancing layer disposed on the barrier layer side of the free magnetic layer includes a first enhancing layer on the barrier layer side and a second enhancing layer on the soft magnetic layer side, and the Fe content of a CoFe alloy constituting the first enhancing layer is specified to be larger than the Fe content of the CoFe alloy of the second enhancing layer.