Thin Film Magnetic Head Shield Bias and Noise Suppression
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Solution Overview
Problem
Existing thin film magnetic heads face challenges in applying sufficient bias to free layers while maintaining side shield functionality, particularly in high-density recording, where magnetic information from adjacent tracks is read, leading to noise issues.
Innovation Solution
Incorporating a pair of shields with an anisotropy providing layer that magnetizes one shield in a desired direction, allowing soft magnetic layers to apply a bias magnetic field to the MR film, which is then absorbed by the shields to effectively shield magnetic fields in the track width direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If soft magnetic layers are disposed on both sides of the MR element to suppress side-reading noise, then the side reading problem is solved, but the bias magnetic field application to the free layer becomes insufficient
Solution Approach 1:
The patent combines the side shield function (absorbing magnetic flux from adjacent tracks) and the bias magnetic field application function into a single integrated structure. The soft magnetic layers are magnetically connected to the first shield, allowing them to be simultaneously magnetized in the track width direction for noise suppression and in the film surface orthogonal direction for bias application, resolving the contradiction between these two functions
Solution Approach 2:
The soft magnetic layers serve multiple functions: they act as side shields to absorb magnetic flux from adjacent tracks (noise suppression) and simultaneously function to apply bias magnetic field to the free layer when magnetized in the film surface orthogonal direction. This multi-functionality resolves the contradiction by making the same structure perform both previously separate roles
2Measurement precision
If the free layer is formed as a single domain layer to improve linearity and suppress Barkhausen noise, then measurement precision is improved, but the device complexity increases due to additional bias magnetic layer requirements
Solution Approach 1:
The patent merges the bias magnetic layer function with the side shield structure. The soft magnetic layers, when magnetized in the film surface orthogonal direction through magnetic connection to the first shield, provide the necessary bias magnetic field to form the free layer as a single domain layer, thereby achieving improved measurement precision without adding separate bias magnetic layer components
Solution Approach 2:
The soft magnetic layers serve dual purposes: suppressing side-reading noise through magnetic flux absorption in the track width direction, and applying bias magnetic field in the film surface orthogonal direction to create a single domain free layer. This multi-functionality achieves the desired measurement precision improvement without increasing 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 ensures efficient absorption of magnetic fields, maintaining the function of side shields and applying sufficient bias to the free layers, thereby improving the linearity of resistance variation and reducing Barkhausen noise.
Implementation Method 1
an anisotropy providing layer that provides exchange anisotropy to a first shield of the pair of shields in order to magnetize the first shield in a desired direction
Implementation Method 2
the soft magnetic material absorbs magnetic flux from adjacent tracks, the effect of noise due to the magnetic flux from the adjacent tracks is suppressed
Implementation Method 3
The bias magnetic layers apply a bias magnetic field to the free layer such that the free layer is formed as a single domain layer
Implementation Method 4
a magneto resistance effect film of which electrical resistance varies corresponding to an external magnetic field
Data Source
AI summary
A thin film magnetic head includes: a magneto resistance effect film of which electrical resistance varies corresponding to an external magnetic field; a pair of shields provided on both sides in a manner of sandwiching the MR film in a direction that is orthogonal to a film surface of the MR film; an anisotropy providing layer that provides exchange anisotropy to a first shield of the pair of shields in order to magnetize the first shield in a desired direction, and that is disposed on the opposite side from the MR film with respect to the first shield; and side shields that are disposed on both sides of the MR film in a track width direction and that include soft magnetic layers magnetically connected with the first shield.