CPP Magnetoresistive Device Orthogonal Magnetization Control
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Solution Overview
Problem
Conventional magnetoresistive devices face challenges in maintaining stable magnetization directions of free layers, leading to erratic magnetization and difficulty in reducing device size, which hinders the achievement of ultra-high recording densities.
Innovation Solution
A magnetoresistive device with a CPP structure, featuring a nonmagnetic intermediate layer and ferromagnetic layers with sensor and magnetization direction control areas, where the magnetization directions of the ferromagnetic layers are antiparallel and controlled by biasing layers to intersect orthogonally, ensuring stable magnetization and reduced device height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the magnetoresistive device uses a simple triple-layer structure to reduce height, then the device height is reduced, but the magnetization directions of free layers become unstable and erratic
Solution Approach 1:
The device is segmented into distinct functional areas: sensor areas for detection and magnetization direction control areas for stabilization. The control areas extend rearward from the sensor areas, creating separate zones that can be independently optimized. This segmentation allows the control areas to provide stable magnetization reference without interfering with the sensor areas' detection function, resolving the contradiction between height reduction and magnetization stability.
Solution Approach 2:
A magnetization direction control multilayer arrangement is introduced as an intermediary element between the fixed magnetization layer and the free layers. This multilayer arrangement includes exchange coupling transfer layers and fixed magnetization layers that mediate the magnetic interaction, providing stable reference directions to the free layers without requiring increased device height. The intermediary structure enables stable magnetization control while maintaining the compact CPP-GMR device geometry.
2Stability of the object's composition
If permanent magnets are added to adjust magnetization directions, then magnetization direction control is improved, but device size increases and magnetic flux leaks toward shield layers
Solution Approach 1:
The external permanent magnets are extracted from the device structure and replaced with integrated magnetization direction control layers formed within the CPP-GMR device itself. The control multilayer arrangement uses thin-film exchange coupling and pinned layers to provide the necessary magnetization direction control, eliminating the need for separate permanent magnet components. This extraction resolves the contradiction by achieving magnetization control without increasing device volume or causing magnetic flux leakage to shield layers.
Solution Approach 2:
The magnetization direction control multilayer arrangement serves multiple functions simultaneously: it provides stable reference magnetization directions, enables exchange coupling to free layers, and integrates within the existing device structure. This multi-functional design achieves effective magnetization control without requiring additional space-consuming components, resolving the contradiction between control quality and device size.
3Ease of manufacture
If the device structure is simplified to reduce height, then manufacturing becomes easier, but reliability of magnetization detection decreases
Solution Approach 1:
Magnetization direction control areas are formed preliminarily extending rearward from sensor areas, establishing stable reference magnetization directions before detection occurs. The control multilayer arrangement is pre-configured with exchange coupling and pinned layers that set the initial magnetization states. This preliminary action ensures reliable detection by preparing stable reference conditions in advance, while maintaining the simplified CPP-GMR structure for ease of manufacture.
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 stabilizes magnetization directions, enhances reliability, and allows for narrower read gaps, thereby improving linear recording densities and meeting demands for ultra-high recording densities.
Implementation Method 1
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.
Implementation Method 2
This is now a GMR device with the CPP (current perpendicular to plane) structure (CPP-GMR device)
Implementation Method 3
said sensor area is provided at both width direction ends with biasing layers working such that the mutually antiparallel magnetizations of said first and second ferromagnetic layers intersect in substantially orthogonal directions
Data Source
AI summary
A magnetoresistive device with CPP structure, comprising a nonmagnetic intermediate layer, and a first ferromagnetic layer and a second ferromagnetic layer stacked and formed with said nonmagnetic intermediate layer interposed between them, wherein each of said first and second ferromagnetic layers comprises a sensor area joining to the nonmagnetic intermediate layer and a magnetization direction control area that extends further rearward from the position of the rear end of said nonmagnetic intermediate layer; a magnetization direction control multilayer arrangement is interposed at an area where the magnetization direction control area for said first ferromagnetic layer is opposite to the magnetization direction control area for said second ferromagnetic layer to produce magnetizations of the said first and second ferromagnetic layers which are antiparallel with each other; and said sensor area is provided at both width direction ends with biasing layers working such that the mutually antiparallel magnetizations of said first and second ferromagnetic layers intersect in substantially orthogonal directions.