Magnetic Sensor Stack Body with Perpendicular Crystal Orientation
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Solution Overview
Problem
The miniaturization of magnetoresistive (MR) elements in hard disk drives leads to a decrease in the bias magnetic field, causing noise and sensitivity issues due to the reduction in the thickness of the hard bias stack body and the complexity of orienting crystal c-axes in the magnetic layer to effectively condense magnetic fluxes on the junction wall surface.
Innovation Solution
A magnetic sensor stack body is designed with first and second magnetic layers where the crystal c-axes of the first layer are oriented almost perpendicular to the junction wall surface, and the second layer's c-axes are randomly distributed, using specific film forming angles to ensure effective magnetic flux condensation, thereby maintaining a uniform magnetic field and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the MR element is miniaturized to increase recording density, then the linear resolution and sensitivity to track edge improve, but the bias magnetic field decreases causing noise and sensitivity issues
Solution Approach 1:
The patent applies different crystal orientations to different regions of the magnetic layer. Specifically, the magnetic layer has a first region with c-axes oriented perpendicular to the junction wall surface and a second region with c-axes oriented in other directions. This local differentiation allows the junction wall surface region to effectively condense magnetic flux while other regions provide additional magnetic field support, resolving the contradiction between miniaturization and bias magnetic field maintenance.
2Volume of moving object
If the thickness of the hard bias stack body is reduced due to miniaturization, then the read head size decreases, but the bias magnetic field becomes insufficient
Solution Approach 1:
The patent changes the crystal orientation parameter of the magnetic layer to perpendicular orientation relative to the junction wall surface in the first region. This parameter change increases the magnetic flux condensation efficiency, allowing the thinner hard bias stack body to generate sufficient bias magnetic field despite the reduced thickness, thus resolving the contradiction between miniaturization and bias field sufficiency.
3Volume of moving object
If the magnetic layer and shield layer are positioned close to each other to reduce size, then the read head becomes more compact, but leakage magnetic flux increases and bias magnetic field decreases
Solution Approach 1:
The patent creates a localized region with perpendicular crystal orientation at the junction wall surface where the magnetic layer contacts the shield layer. This local quality change in crystal orientation enhances magnetic flux condensation at the critical interface region, reducing leakage magnetic flux despite the close positioning of the magnetic layer and shield layer, thus resolving the contradiction between compactness and leakage reduction.
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 enhances the uniformity of the magnetic field across the free layer, improving sensitivity and reducing noise in the read head, even at reduced stripe heights, by effectively condensing magnetic fluxes onto the junction wall surface.
Implementation Method 1
the crystal c-axes in the first magnetic layer are aligned and oriented along an ABS in a film plane... effectively condensing magnetic fluxes on the junction wall surface
Implementation Method 2
an MR head using an element whose electric resistance changes according to fluctuations in external magnetic fields
Data Source
AI summary
The present invention is directed to align crystal c-axes in magnetic layers near two opposed junction wall surfaces of a magnetoresistive element so as to be almost perpendicular to the junction wall surfaces. A magnetic sensor stack body has, on sides of opposed junction wall surfaces of a magnetoresistive element, field regions for applying a bias magnetic field to the element. The field region has first and second magnetic layers having magnetic particles having crystal c-axes, the first magnetic layer is disposed adjacent to the junction wall surface in the field region, the crystal c-axes in the first magnetic layer are aligned and oriented along an ABS in a film plane, the second magnetic layer is disposed adjacent to the first magnetic layer in the field region, and the crystal c-axis directions in the second magnetic layer are distributed at random in a plane.