Trilayer MR Sensor Orthogonal Biasing for Sensitivity
Solution Overview
Problem
Current trilayer magnetoresistive sensors face challenges in achieving enhanced sensitivity and control over magnetic response to external fields due to limitations in magnetization biasing configurations, particularly in minimizing shield-to-shield spacing and maximizing areal density.
Innovation Solution
A trilayer sensor design with two free ferromagnetic layers separated by a nonmagnetic spacer layer, where one layer is biased with a high coercivity magnet and the other with a high moment magnet, both positioned such that their magnetizations are substantially orthogonal, allowing for greater sensitivity and response to magnetic fields without antiferromagnetic pinning or synthetic antiferromagnetic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single free layer magnetoresistive sensors are used, then the device complexity is low, but the sensitivity and control over magnetic response to external fields are limited
Solution Approach 1:
The patent divides the single free layer into two separate free ferromagnetic layers (first and second free layers) with different magnetization orientations. Each layer is independently biased by dedicated bias magnets, allowing separate control of magnetic responses. This segmentation enables enhanced sensitivity to different field components while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
The patent transitions from a single-layer planar structure to a trilayer structure with out-of-plane magnetization in one free layer and in-plane magnetization in the other. This dimensional change in magnetization orientation (from purely in-plane to combining in-plane and out-of-plane components) provides additional degrees of freedom for controlling magnetic response and enhancing sensitivity to three-dimensional magnetic fields.
2Area of stationary object
If shield-to-shield spacing is minimized to increase areal density, then the areal density increases, but the control over magnetic response to external fields becomes more difficult
Solution Approach 1:
The patent applies different biasing configurations to different regions of the sensor structure. The first free layer has in-plane magnetization biased by first bias magnets, while the second free layer has out-of-plane magnetization biased by second bias magnets. This local differentiation of magnetic properties and biasing strategies allows each layer to be optimized for specific detection functions, maintaining ease of control even when shield-to-shield spacing is minimized for increased areal 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 enhances the sensor's sensitivity and control over magnetic responses, leading to improved detection capabilities and increased areal density without the need for antiferromagnetic pinning or synthetic structures, thereby optimizing magnetic field interactions.
Implementation Method 1
One free layer is biased with a high coercivity magnet positioned adjacent the layer and the other free layer is biased with a high moment magnet positioned adjacent that layer. The layers are biased such that the magnetizations of both layers are substantially orthogonal to each other.
Implementation Method 2
One free layer is biased with a high coercivity magnet positioned adjacent the layer
Implementation Method 3
A trilayer magnetoresistive sensor is generally described
Data Source
AI summary
A trilayer magnetoresistive sensor has at least first and second ferromagnetic layers separated by a nonmagnetic layer. A high coercivity permanent magnet bias element biases the first ferromagnetic layer in a first direction. A high moment permanent magnet bias element biases the second ferromagnetic layer in a second direction substantially orthogonal to the first direction.