Recessed Reference Layer Magnetic Sensor Shield Spacing
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Solution Overview
Problem
Current magnetic sensors face challenges in optimizing the magnetization direction and shield configuration to enhance sensing efficiency and areal density, particularly in reducing shield-to-shield spacing while maintaining effective electrical insulation and magnetic coupling control.
Innovation Solution
The magnetic sensor design incorporates a free sub-stack with magnetization perpendicular to the plane, a recessed reference sub-stack, and a front shield positioned between the reference sub-stack and the air bearing surface, utilizing specific layer configurations and materials like TbFeCo, CoFeB, and soft magnetic materials for shields to achieve perpendicular magnetization and efficient signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the reference layer assembly is recessed from the air bearing surface, then the shield-to-shield spacing is reduced and areal density is increased, but the magnetic coupling and electrical insulation between layers become more difficult to maintain
Solution Approach 1:
The reference layer assembly is recessed from the air bearing surface into a second recess, creating a vertical dimension change that reduces the horizontal shield-to-shield spacing while maintaining layer separation. This dimensional reconfiguration allows reduced areal density without compromising magnetic coupling or electrical insulation between the free and reference layer assemblies.
Solution Approach 2:
A nonmagnetic spacer layer is positioned between the free layer assembly and reference layer assembly, serving as an intermediary that maintains electrical insulation and magnetic coupling control. The spacer layer fills the gap created by the recessed configuration, ensuring reliable layer separation while allowing the shield-to-shield spacing to be reduced for increased areal density.
2Productivity
If a front shield is positioned between the reference sub-stack and the air bearing surface, then media flux flow and reader efficiency are enhanced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The front shield serves multiple functions simultaneously: it enhances media flux flow to the sensor, provides electrical insulation, and defines the air bearing surface geometry. By consolidating these functions into a single component, the patent reduces overall device complexity despite the recessed reference layer configuration.
Solution Approach 2:
The front shield is integrated with the recess structure, merging the shield function with the mechanical support and positioning features. This integration reduces the number of separate components and simplifies manufacturing, while still achieving enhanced media flux flow and reader efficiency.
3Measurement precision
If the free layer assembly extends to the air bearing surface with perpendicular magnetization, then sensing efficiency is improved, but the control of magnetization direction and magnetic coupling becomes more challenging
Solution Approach 1:
The patent employs perpendicular magnetization in the free layer assembly, changing the magnetization parameter from in-plane to out-of-plane orientation. This parameter change enhances sensing efficiency by improving media flux detection, while the synthetic antiferromagnetic coupling and spacer layer configuration maintain controlled magnetic coupling between layers.
Solution Approach 2:
The free layer assembly uses composite material structures including CoFeB and TbFeCo layers with specific thicknesses and compositions. These composite materials provide perpendicular magnetic anisotropy that stabilizes the magnetization direction, improving sensing efficiency while making magnetization control more manageable through material property engineering.
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 shield-to-shield spacing, increases areal density, and enhances media flux and electrical current flow, leading to improved reader efficiency and signal output by optimizing the magnetic circuit and electrical insulation.
Implementation Method 1
MR sensor 10 includes bottom shield 12, seedlayer 14, freelayer assembly 16 (formed by freelayers 17 and 19), spacer layer 20, reference layer assembly 22 (formed by reference layer 24, nonmagnetic layer 26, pinned layer 27, antiferromagnetic layer 28, and cap layer 29)... the magnetization direction of freelayer assembly 16 will change in relation to the fixed magnetization of reference layer 24 of reference layer assembly 22 and will be detected as a change in electrical resistance
Implementation Method 2
Front shield 32 is separated from reference layer assembly 22 and spacer layer 20 by insulator layer 34
Implementation Method 3
The freelayer assembly has a magnetization direction substantially perpendicular to the planar orientation of the layer... Second freelayer 19 also exhibits magnetization direction perpendicular to the planar orientation of the layer
Data Source
AI summary
A magnetic sensor has at least a free sub-stack, a reference sub-stack and a front shield. The free sub-stack has a magnetization direction substantially perpendicular to the planar orientation of the layer and extends to an air bearing surface. The reference sub-stack has a magnetization direction substantially perpendicular to the magnetization direction of the free sub-stack. The reference sub-stack is recessed from the air bearing surface and a front shield is positioned between the reference sub-stack and the air bearing surface.