CPP Magnetic Sensor Free Layer Stack Side Shields
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Solution Overview
Problem
Conventional CPP magnetic field detecting elements face limitations in reducing the gap between shields and effective track width due to the requirement of synthetic pinned layers and antiferromagnetic layers, which restricts the achievement of high recording density and narrow track width.
Innovation Solution
A CPP type magnetic field detecting element with a stack configuration including two free layers and a bias magnetic field layer on the backside, eliminating the need for synthetic pinned and antiferromagnetic layers, and incorporating side shield layers to reduce the effective track width and gap between shields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If synthetic pinned layers and antiferromagnetic layers are used to fix magnetization direction, then magnetization stability is improved, but stack thickness increases and recording density deteriorates
Solution Approach 1:
The patent removes the antiferromagnetic layer and synthetic pinned layer structure from the conventional CPP element. Instead of using exchange-coupled pinned layers with antiferromagnetic coupling, the invention uses a simplified single free layer configuration where the magnetization direction is controlled by geometric magnetocrystalline anisotropy and stress-induced anisotropy, eliminating the need for thick antiferromagnetic layers while maintaining magnetization stability.
Solution Approach 2:
The patent changes the mechanism for fixing magnetization direction from exchange-coupling with antiferromagnetic layers to using geometric magnetocrystalline anisotropy and stress-induced anisotropy. By controlling the shape, size, and stress state of the free layer, the magnetization direction is stabilized without requiring thick antiferromagnetic layers, thus reducing stack thickness while maintaining stability.
2Productivity
If shield layers are placed close together to reduce gap, then recording density is improved, but magnetic field shielding effectiveness deteriorates
Solution Approach 1:
The patent introduces side shield layers positioned laterally adjacent to the free layer, which pre-shield the magnetic field from adjacent tracks before it reaches the detection region. This preliminary shielding action allows the main shield layers to be placed closer together while still maintaining effective magnetic field isolation, thus enabling higher recording density without sacrificing shielding effectiveness.
Solution Approach 2:
The patent adds shielding in the lateral dimension by introducing side shield layers, rather than relying solely on the vertical arrangement of shield layers. This dimensional expansion of the shielding structure provides additional magnetic field isolation pathways, allowing reduced gap between main shields while maintaining shielding effectiveness for higher recording density.
3Productivity
If effective track width is reduced for higher density, then recording density is improved, but signal detection capability deteriorates
Solution Approach 1:
The patent optimizes the local magnetic properties and geometry of the free layer to enhance magnetoresistance effect within the narrowed track width. By controlling the thickness, composition, and stress state of the free layer locally, the signal output is maximized despite the reduced effective track width, maintaining detection capability while achieving higher recording density.
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 allows for a significant reduction in stack thickness and effective track width, enabling higher recording density and improved magnetic field detection capabilities.
Implementation Method 1
a bias magnetic layer which is provided on a surface of said stack, the surface being opposite to an air bearing surface of said stack, wherein said bias magnetic layer applies a bias magnetic field to said upper magnetic layer and to said lower magnetic layer in a direction perpendicular to the air bearing surface
Implementation Method 2
magnetization directions of said upper magnetic layer and said lower magnetic layer change in accordance with an external magnetic field
Implementation Method 3
an upper shield electrode layer and a lower shield electrode layer which are provided in a manner that they sandwich said stack therebetween in a direction of stacking of said stack, wherein said upper shield electrode layer and said lower shield electrode layer supply sense current in the direction of stacking and magnetically shield said stack
Implementation Method 4
GMR (Giant Magneto Resistance) elements are known
Data Source
AI summary
A magnetic field detecting element comprising: a stack including an upper magnetic layer, a lower magnetic layer and a non-magnetic intermediate layer sandwiched between said upper magnetic layer and said lower magnetic layer, wherein magnetization directions of said upper magnetic layer and said lower magnetic layer change in accordance with an external magnetic field; an upper shield electrode layer and a lower shield electrode layer which are provided in a manner that they sandwich said stack therebetween in a direction of stacking of said stack, wherein said upper shield electrode layer and said lower shield electrode layer supply sense current in the direction of stacking and magnetically shield said stack; a bias magnetic layer which is provided on a surface of said stack, the surface being opposite to an air bearing surface of said stack, wherein said bias magnetic layer applies a bias magnetic field to said upper magnetic layer and to said lower magnetic layer in a direction perpendicular to the air bearing surface; and a pair of side shield layers which are provided on both sides of said stack with regard to a track width direction.