CPP Magnetoresistive Device Insulating Shield Layers
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Solution Overview
Problem
Current magnetoresistive devices face challenges in achieving ultra-high recording densities due to limitations in narrowing the read gap length and maintaining strong exchange coupling between ferromagnetic layers, leading to instability and reliability issues, especially with the need for antiferromagnetic layers that increase device size and complexity.
Innovation Solution
A magnetoresistive device with a CPP structure, where a magnetoresistive unit is sandwiched between shield layers with joining layers and a nonmagnetic insulating layer, allowing for anti-parallel magnetization control without the need for antiferromagnetic layers, thereby stabilizing the shield domains and improving recording density and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If insulating layers are removed to achieve narrower read gap length, then recording density is improved, but exchange coupling between ferromagnetic layers deteriorates
Solution Approach 1:
A nonmagnetic insulating layer is introduced as an intermediary between the first and second shield layers. This insulating layer prevents direct electrical contact while maintaining magnetic coupling through the shield layers, thereby enabling narrow read gap lengths without compromising the exchange coupling stability between ferromagnetic layers.
Solution Approach 2:
The shield structure is segmented into first and second shield layers separated by a nonmagnetic insulating layer. This segmentation allows independent optimization of each shield layer's function while maintaining overall magnetic coupling, resolving the contradiction between narrow gap requirements and coupling stability.
2Reliability
If antiferromagnetic layers are added to maintain exchange coupling, then coupling strength is improved, but device complexity increases
Solution Approach 1:
The antiferromagnetic layer is extracted from the device structure and replaced by an external bias magnetic field system. This eliminates the need for additional antiferromagnetic material layers while maintaining the required exchange coupling strength between ferromagnetic layers, thereby reducing device complexity.
Solution Approach 2:
The mechanical/structural approach of using antiferromagnetic layers for exchange coupling is substituted with a magnetic field approach. An external bias magnetic field is applied to achieve the same coupling effect, replacing the need for complex multilayer antiferromagnetic structures.
3Productivity
If shield gap is narrowed to increase recording density, then productivity is improved, but heat dissipation deteriorates
Solution Approach 1:
The nonmagnetic insulating layer acts as a thermal intermediary between the shield layers. It provides a thermal conduction path that facilitates heat dissipation from the magnetoresistive device while maintaining the narrow electrical gap required for high recording density, thereby resolving the contradiction between productivity and energy loss.
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 enables a narrower read gap length and stable magnetoresistive changes, enhancing the reliability and performance of the device by maintaining anti-parallel magnetization states between ferromagnetic layers, thus meeting demands for ultra-high recording densities.
Implementation Method 1
The magnetoresistive device (CPP-GMR device) of the so-called CPP (current perpendicular to plane) structure
Implementation Method 2
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 3
a recording head having a write-only induction type magnetic device
Data Source
AI summary
The invention provides a magnetoresistive device of the CPP (current perpendicular to plane) structure, comprising a magnetoresistive unit, and a first shield layer and a second shield layer which are located and formed such that the magnetoresistive unit is sandwiched between them from above and below, with a sense current applied in the stacking direction, wherein said magnetoresistive unit comprises a non-magnetic intermediate layer, and a first ferromagnetic layer and a second ferromagnetic layer stacked and formed such that said nonmagnetic intermediate layer is sandwiched between them.