CPP GMR Device with Split Ferromagnetic Layer
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Solution Overview
Problem
Current magneto-resistive effect devices face challenges in achieving ultra-high recording densities due to limitations in device size and reliability, leading to issues with unneeded information being written on the medium and erratic operation from external magnetic fields.
Innovation Solution
A CPP structure magneto-resistive effect device with a nonmagnetic intermediate layer sandwiched between antiparallel ferromagnetic layers, where the second ferromagnetic layer is divided into front and rear portions, and a bias magnetic field is applied to enhance sensitivity and stability, reducing the impact of external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the device area is decreased to achieve narrower tracks and higher recording density, then the recording density is improved, but the heat dissipation efficiency decreases and reliability deteriorates
Solution Approach 1:
The patent transitions from a planar CIP-GMR device structure to a vertical CPP-GMR device structure. By changing the current flow direction from in-plane to perpendicular-to-plane, the device achieves higher recording density through reduced footprint while maintaining adequate operating current capability through the vertical current path, thus resolving the contradiction between density and reliability.
2Quantity of substance
If the reproducing gap is narrowed to increase recording density, then the linear recording density is improved, but the device becomes more susceptible to external magnetic fields causing erratic operation
Solution Approach 1:
The patent divides the single ferromagnetic layer into multiple ferromagnetic layers separated by nonmagnetic intermediate layers. This segmentation creates a spin valve structure where each layer can be independently controlled, allowing the device to achieve narrow gap for high density while the multi-layer configuration provides magnetic field shielding and reduced susceptibility to external interference.
Solution Approach 2:
The patent employs a composite multilayer structure consisting of alternating ferromagnetic and nonmagnetic layers. This composite structure combines the benefits of narrow gap (from the layered configuration) with enhanced magnetic field rejection (from the nonmagnetic intermediate layers), resolving the contradiction between density and susceptibility to external fields.
3Volume of moving object
If a simple triple-layer structure is used to slim down the device, then the device height is reduced, but unneeded information is written on the medium due to insufficient magnetic field control
Solution Approach 1:
The patent segments the ferromagnetic layer into multiple layers with distinct magnetic properties. The first ferromagnetic layer has fixed magnetization direction while the second ferromagnetic layer has variable magnetization direction. This segmentation enables precise magnetic field control that prevents unwanted writing while maintaining slim device profile through the vertical layered structure.
Solution Approach 2:
The patent assigns different magnetic characteristics to different layers: the first ferromagnetic layer is designed with fixed magnetization (through exchange coupling with antiferromagnetic layer) while the second layer maintains variable magnetization. This local differentiation of magnetic properties enables the slim device to control magnetic field precisely, preventing unwanted information writing on the medium.
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 narrower read gaps, improved linear recording densities, and enhanced operational stability by minimizing unwanted information writing and reducing the device's susceptibility to external magnetic fields.
Implementation Method 1
the first ferromagnetic layer and the second ferromagnetic layer are magnetically coupled via the nonmagnetic intermediate layer such that the magnetizations of the first ferromagnetic layer and the second ferromagnetic layer are antiparallel with each other
Implementation Method 2
a magneto-resistive effect device adapted to read the magnetic field intensity of magnetic recording media or the like as signals
Implementation Method 3
The fixation of the direction of magnetization of the first ferromagnetic layer is achieved by the exchange coupling of it with an antiferromagnetic layer provided adjacent to it, whereby unidirectional anisotropic energy (also called the 'exchange bias' or 'coupled magnetic field') is applied to the first ferromagnetic layer
Data Source
AI summary
A magneto-resistive effect device of a CPP structure includes a nonmagnetic intermediate layer, and a first ferromagnetic layer and a second ferromagnetic layer stacked together and formed with the nonmagnetic intermediate layer sandwiched between them. The first ferromagnetic layer and the second ferromagnetic layer are magnetically coupled via the nonmagnetic intermediate layer such that magnetizations of the first ferromagnetic layer and the second ferromagnetic layer are antiparallel with each other. Mutually antiparallel magnetizations of two magnetic layers lie in a medium opposite plane or front to rear direction and in a rear to front direction. The second ferromagnetic layer is divided by a nonmagnetic intervening layer into a front second ferromagnetic layer and a rear second ferromagnetic layer on the way from the front to the rear.