Magnetoresistive Element Bias Field Leakage Control
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Solution Overview
Problem
Conventional magnetoresistive elements with a three-layer structure face issues with asymmetry in output and low yield due to inadequate bias magnetic field application, particularly because of low saturation magnetization and magnetic field leakage, which affects the reliability of magnetic disk drives.
Innovation Solution
A magnetoresistive element with a specific structure including a first and second ferromagnetic layer, a spacer layer, a bias magnetic field applying layer with high saturation magnetization, and a buffer layer, where the bias magnetic field applying layer is positioned between the shields and the MR stack, and the high saturation magnetization layer is not between the shield and the hard magnetic layer, effectively applying the bias magnetic field while minimizing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias magnetic field applying layer with hard magnetic material is used, then the bias magnetic field can be applied to the ferromagnetic layers, but magnetic field leakage occurs to the shields reducing reliability
Solution Approach 1:
A nonmagnetic buffer layer is introduced as an intermediary between the hard magnetic layer and the first shield. This buffer layer acts as a magnetic field barrier that prevents leakage of the bias magnetic field to the first shield, thereby eliminating the harmful magnetic field leakage while maintaining the necessary bias field application to the ferromagnetic layers.
Solution Approach 2:
The bias magnetic field applying layer is segmented into two distinct functional parts: a hard magnetic layer that generates the bias magnetic field, and a nonmagnetic buffer layer that prevents field leakage. This segmentation allows each layer to perform its specific function independently - the hard magnetic layer provides the necessary bias field while the buffer layer blocks leakage to the shield.
2Quantity of substance
If the read gap length is reduced to increase recording density, then higher recording density is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the magnetic field distribution parameters by introducing the nonmagnetic buffer layer, which modifies how the bias magnetic field is distributed in the read gap region. This allows for reduced read gap length while maintaining stable magnetic field conditions that facilitate precise manufacturing control.
3Reliability
If conventional GMR elements are used, then the structure is simple, but the sensitivity and output are insufficient for high recording density
Solution Approach 1:
The MR element employs a composite structure with multiple ferromagnetic layers (first and second ferromagnetic layers with different magnetization directions), a nonmagnetic spacer layer, and a bias magnetic field applying layer with hard magnetic material. This composite structure enables enhanced sensitivity and output by utilizing the combined magnetic effects of multiple layers with different orientations, while the nonmagnetic buffer layer prevents field leakage.
4Reliability
If the bias magnetic field applying layer is positioned close to the MR stack, then effective bias field application is achieved, but magnetic field leakage to shields increases
Solution Approach 1:
The nonmagnetic buffer layer serves as a magnetic field intermediary positioned between the hard magnetic layer and the first shield. It allows the bias magnetic field to effectively reach the MR stack while simultaneously blocking the leakage path to the first shield, thus resolving the contradiction between effective field application and field leakage prevention.
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 reduces variations in output asymmetry and enhances the reliability of magnetic disk drives by stabilizing the bias magnetic field application and preventing degradation of the hard magnetic layer's crystallinity and orientability.
Implementation Method 1
a bias magnetic field applying layer that is disposed at a location between the first and second shields and adjacent to the rear end face, and that applies a bias magnetic field to the first and second ferromagnetic layers
Implementation Method 2
the resistance of the MR element changes. With this read head, it is possible to detect the signal magnetic field by detecting the resistance of the MR element
Implementation Method 3
The antiferromagnetic layer is a layer that fixes the direction of the magnetization of the pinned layer by means of exchange coupling with the pinned layer
Data Source
AI summary
A magnetoresistive element includes a first and a second shield, and an MR stack disposed between the shields. The MR stack includes a first and a second ferromagnetic layer, and a nonmagnetic spacer layer disposed between the ferromagnetic layers. The first and second ferromagnetic layers have magnetizations that are in directions antiparallel to each other when no external magnetic field is applied to the layers, and that change directions in response to an external magnetic field. An insulating layer is formed to touch a rear end face of the MR stack and the first shield, and a bias magnetic field applying layer is formed above the insulating layer with a buffer layer disposed in between. The bias magnetic field applying layer includes a hard magnetic layer and a high saturation magnetization layer. The high saturation magnetization layer is located between the rear end face and the hard magnetic layer, but not located between the first shield and the hard magnetic layer.