CPP Magnetic Detecting Element With Self-Pinned Layer
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Solution Overview
Problem
Current CPP magnetic detecting elements face challenges in enhancing the GMR effect due to spin-independent scattering caused by antiferromagnetic layers and difficulty in fixing the magnetization of the pinned magnetic layer, which limits their ability for high-density recording.
Innovation Solution
A CPP magnetic detecting element structure is developed without antiferromagnetic layers, where the magnetization of the pinned magnetic layer is firmly fixed using uniaxial anisotropy, achieved by incorporating a nonmagnetic material layer with a higher lattice constant than Cu and a magnetostriction-enhancing layer, enhancing the spin-dependent bulk scattering and reducing spin-independent scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antiferromagnetic layers are used to fix the magnetization of the pinned magnetic layer, then the magnetization can be firmly fixed, but spin-independent scattering occurs due to Joule heat generation, reducing the GMR effect
Solution Approach 1:
The patent removes the antiferromagnetic layer from the magnetic detecting element structure. Instead of using antiferromagnetic layers to fix magnetization, the invention uses the uniaxial anisotropy of the pinned magnetic layer itself, achieved by depositing it on a buffer layer with different thermal expansion coefficients. This extraction of the harmful antiferromagnetic layer eliminates the Joule heat generation and spin-independent scattering while maintaining magnetization fixation capability.
Solution Approach 2:
The patent introduces a buffer layer as an intermediary between the substrate and the pinned magnetic layer. This buffer layer, having different thermal expansion coefficients, induces uniaxial anisotropy in the pinned magnetic layer during deposition, thereby fixing the magnetization direction without requiring antiferromagnetic layers. The buffer layer acts as a mediator that enables magnetization fixation through a different physical mechanism.
2Reliability
If the multilayer composite structure is used with antiferromagnetic layers, then the GMR effect can be observed, but the structure becomes complex and difficult to manufacture
Solution Approach 1:
The patent simplifies the multilayer composite structure by removing the antiferromagnetic layers. The GMR effect is maintained through the remaining ferromagnetic and nonmagnetic layer combinations, specifically through spin-dependent bulk scattering in the ferromagnetic layers and spin-dependent interface scattering at the interfaces. This reduction in layers decreases manufacturing complexity while preserving the essential GMR effect.
3Ease of operation
If current flows through the multilayer composite, then the magnetic detecting element can operate, but Joule heat causes lattice vibration and phonon scattering, reducing performance
Solution Approach 1:
The patent eliminates the source of Joule heat by removing the antiferromagnetic layer, which had the highest specific resistance in the stack. Without this high-resistance layer, the overall resistance of the multilayer composite is reduced, minimizing Joule heat generation during current flow. This reduces lattice vibration and phonon scattering, improving the magnetic detecting element's performance.
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 approach increases the GMR effect, improves the reliability of the magnetic detecting element, and allows for higher track density recording by firmly fixing the magnetization of the pinned magnetic layer, reducing distortion and asymmetry in reproduction waveforms.
Implementation Method 1
a nonmagnetic material layer made of a nonmagnetic metal having a lattice constant higher than that of Cu
Implementation Method 2
The magnetization of the pinned magnetic layer is more firmly fixed by the uniaxial anisotropy of the pinned magnetic layer
Implementation Method 3
a magnetostriction-enhancing layer made of a nonmagnetic metal, disposed on the surface opposite to the nonmagnetic material layer of the first magnetic layer
Implementation Method 4
The variation in resistance per unit area (ΔR·A) of the CPP magnetic detecting element is closely related to the spin-dependent bulk scattering effect
Implementation Method 5
At least part of crystals in the magnetostriction-enhancing layer and the first magnetic layer and at least part of crystals in the nonmagnetic material layer and the second magnetic layer are present in an epitaxial state or a heteroepitaxial state
Data Source
AI summary
A CPP magnetic detecting element having a pinned magnetic layer whose magnetization is fixed by its uniaxial anisotropy in a structure that CIP magnetic detecting elements do not allow. In the CPP magnetic detecting element, the upper and lower surfaces of a pinned magnetic layer having an artificial ferrimagnetic structure are disposed between a magnetostriction-enhancing layer made of a nonmagnetic metal and a nonmagnetic material layer having a higher lattice constant than Cu. CPP magnetic detecting elements allow this structure without reducing the variation in resistance per unit area ΔR·A. Thus, the magnetostriction coefficient of the pinned magnetic layer can be increased from above and below, thereby more firmly fixing the magnetization of the pinned magnetic layer.