CPP Magnetoresistive Device Antiparallel Shield Control
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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 stable magnetoresistive effects, particularly in achieving antiparallel magnetization states between ferromagnetic layers without strong exchange coupling, which affects reliability and sensitivity to external magnetic fields.
Innovation Solution
A magnetoresistive device with a CPP structure, featuring a nonmagnetic intermediate layer sandwiched between ferromagnetic layers, with exchange coupling function gap layers and magnetization direction control means to create an antiparallel magnetization state, utilizing CoFe alloy layers with specific magnetostriction properties and exchange coupling materials like Ru, Rh, and Pd to achieve stable orthogonal magnetization directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the read gap length is narrowed to increase recording density, then the recording density is improved, but the heat dissipation efficiency decreases and reliability deteriorates
Solution Approach 1:
The patent changes the magnetization direction parameter from in-plane to perpendicular magnetization in the shield layers, and optimizes the exchange coupling strength parameter between ferromagnetic layers to achieve stable antiparallel magnetization state. This allows narrower read gap while maintaining sufficient heat dissipation and operational reliability through enhanced magnetic field control
2Measurement precision
If the exchange coupling strength is reduced to achieve antiparallel magnetization state, then the sensitivity to external magnetic fields is improved, but the stability of magnetization state deteriorates
Solution Approach 1:
The patent uses composite magnetic layer structures with alternating ferromagnetic and nonmagnetic layers, where the ferromagnetic layers have perpendicular magnetization and are coupled through the nonmagnetic intermediate layer. This composite structure enables controlled exchange coupling that maintains stable antiparallel magnetization while preserving sensitivity to external magnetic fields for accurate signal detection
3Quantity of substance
If the device area is reduced to narrow the track width, then the recording density is improved, but the heat dissipation efficiency decreases
Solution Approach 1:
The patent changes the magnetization orientation parameter to perpendicular magnetization in shield layers and optimizes the exchange coupling parameter between ferromagnetic layers. This enables more efficient magnetic field confinement and signal detection in smaller device areas, reducing the energy dissipated as heat while maintaining high recording density through improved magnetic field utilization
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 gap lengths and improved reliability by maintaining stable magnetoresistive effects and reducing MR ratio fluctuations, even with variations in bias magnetic field intensity, enhancing the device's sensitivity and operational reliability.
Implementation Method 1
said first ferromagnetic layer and said second ferromagnetic layer each contain a CoFe alloy layer having a positive magnetostriction property with a magnetostriction λ in the range of 20×10−6 to 40×10−6
Implementation Method 2
said first ferromagnetic layer and said second ferromagnetic layer are exchange coupled to said first shield layer and said second shield layer, respectively, by way of a first exchange coupling function gap layer and a second exchange coupling function gap layer
Implementation Method 3
a magnetoresistive device adapted to read the magnetic field intensity of magnetic recording media or the like as signals
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 with a sense current applied in a stacking direction. The magnetoresistive unit comprises a nonmagnetic intermediate layer, and a first ferromagnetic layer and a second ferromagnetic layer stacked and formed such that the nonmagnetic intermediate layer is sandwiched between them. The first shield layer and the second shield layer are each controlled by magnetization direction control means in terms of magnetization direction to create an antiparallel magnetization state where their magnetizations are in opposite directions. The first ferromagnetic layer and the second ferromagnetic layer are exchange coupled to the first shield layer and the second shield layer, respectively, by way of a first exchange coupling function gap layer and a second exchange coupling function gap layer, with an exchange coupled strength of 0.2 to 2.5 erg/cm2.