Magnetoresistive Device Bulk Scattering Reduction
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Solution Overview
Problem
Conventional synthetic type CPP-GMR devices experience a reduction in the amount of resistance change due to their structural characteristics, leading to a loss in the magnetoresistive effect, which hinders the ability to respond to increased recording densities.
Innovation Solution
A magnetoresistive device with a first magnetization fixed layer and a second magnetization fixed layer antiferromagnetically coupled, where the second layer has a bulk scattering coefficient of 0.25 or less, and a magnetization free layer is positioned opposite to the second magnetization fixed layer, allowing a sense current to flow perpendicular to the laminate surface, thereby minimizing the bulk scattering effect and enhancing the resistance change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a synthetic type CPP-GMR device is used with a magnetization fixed layer having a three-layer structure including two ferromagnetic films with antiparallel magnetization directions, then the magnetization direction stability is improved and net moment is reduced, but the amount of resistance change is reduced due to the bulk scattering effect
Solution Approach 1:
The patent applies local quality by differentiating the bulk scattering coefficients of the two ferromagnetic films in the synthetic magnetization fixed layer. The first ferromagnetic film has a bulk scattering coefficient of greater than 0.25, while the second ferromagnetic film has a bulk scattering coefficient of 0.25 or less. This local differentiation allows the second film to minimize the bulk scattering effect and preserve the magnetoresistive effect, while the overall antiparallel structure maintains magnetization stability.
Solution Approach 2:
The patent changes the bulk scattering coefficient parameter of the ferromagnetic films to resolve the contradiction. By selecting materials or compositions with different bulk scattering coefficients (greater than 0.25 for the first film, 0.25 or less for the second film), the patent optimizes both the magnetization stability and the resistance change amount. This parameter change enables the second film to contribute minimally to bulk scattering while maintaining the antiparallel coupling for stability.
2Productivity
If the dimension in reproducing track width is reduced to respond to higher recording density, then the output of CIP-GMR device is reduced, but CPP-GMR device maintains higher output
Solution Approach 1:
The patent changes the current flow direction parameter from in-plane (CIP) to perpendicular-to-plane (CPP) relative to the laminate surface. This parameter change allows the device to maintain higher output voltage even when the reproducing track width dimension is reduced, thereby responding effectively to higher recording densities without sacrificing output power.
3Device complexity
If a sense current flows in an in-plane direction (CIP-GMR), then the device structure is simpler, but the magnetic sensitive portion becomes minute with decreased dimension, reducing voltage change
Solution Approach 1:
The patent transitions the current flow from the in-plane dimension (CIP) to the perpendicular-to-plane dimension (CPP). This dimensional change allows the sense current to flow through the laminate thickness rather than along the plane, maintaining a larger effective magnetic sensitive portion even when track width dimensions are reduced. This resolves the contradiction by preserving voltage change amount while adapting to higher recording density requirements.
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 improves the magnetoresistive ratio by preventing the reduction in resistance change, enabling the device to respond to higher recording densities and maintain stability in magnetization direction, thus enhancing the detection of signal magnetic fields.
Implementation Method 1
the second magnetization fixed film farther from the magnetization free layer out of the first magnetization fixed film and the second magnetization fixed film has a bulk scattering coefficient of 0.25 or less, so a bulk scattering effect by the second magnetization fixed film which has a function of canceling out the amount of resistance change between the magnetization free layer and the first magnetization fixed film can be prevented
Implementation Method 2
a first magnetization fixed layer including a first magnetization fixed film having a magnetization direction fixed in a predetermined direction and a second magnetization fixed film being antiferromagnetically coupled to the first magnetization fixed film
Implementation Method 3
a magnetoresistive device exhibiting a giant magnetoresistive effect
Data Source
AI summary
Provided are a magnetoresistive device capable of obtaining a larger amount of resistance change and responding to a higher recording density and a thin film magnetic head comprising the magnetoresistive device. A first magnetization fixed film and a second magnetization fixed film have magnetization directions antiparallel to each other, and the second magnetization fixed film farther from a magnetization free layer is made of, for example, a material including at least one selected from the group consisting of tantalum (Ta), chromium (Cr) and vanadium (V), and has a bulk scattering coefficient of 0.25 or less. Thereby, a bulk scattering effect by the second magnetization fixed film which has a function of canceling out the amount of resistance change between the magnetization free layer and the first magnetization fixed film can be prevented, and a magnetoresistive ratio ΔR/R can be improved, and recorded magnetic information with a higher recording density can be read out.