CPP-GMR Element Semiconductor Spacer Epitaxial Growth
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Solution Overview
Problem
Current CPP-GMR elements have a relatively low magnetoresistive ratio, which limits their effectiveness for high-density magnetic recording applications, and they also face issues with increased area resistivity and local current migration due to high current density.
Innovation Solution
A CPP-GMR element with a semiconductor spacer layer formed through epitaxial growth, where the first and second ferromagnetic layers are laminated to sandwich the spacer layer, and the semiconductor layer is configured with a cubical crystal structure, such as zincblende or rock salt type, to enhance the magnetoresistive ratio while maintaining low area resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional CPP-GMR element with metal spacer layer is used, then heat dissipation efficiency is improved, but magnetoresistive ratio is insufficient
Solution Approach 1:
The patent changes the material parameter of the spacer layer from conventional metal (Cu, Ag, Al) to semiconductor material (Si, Ge, Sn, or their alloys) with controlled carrier concentration. This parameter change enables simultaneous achievement of high magnetoresistive ratio (50% or more) and adequate heat dissipation, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent employs composite structure by combining ferromagnetic layers with semiconductor spacer layer. The semiconductor material acts as an intermediate layer that provides both electrical resistance for high GMR effect and thermal conduction for heat dissipation, creating a composite functional system that overcomes the limitations of pure metal or pure insulator spacer layers.
2Productivity
If the cross sectional area of the element is reduced for narrower track width, then recording density is improved, but resistance value increases
Solution Approach 1:
By changing the spacer layer material to semiconductor with optimized carrier concentration, the patent achieves high magnetoresistive ratio that compensates for the increased resistance due to reduced cross-sectional area. This allows narrower track width implementation while maintaining acceptable resistance levels for practical applications.
3Power
If high current density is applied to improve operating current, then output signal is improved, but local current migration occurs
Solution Approach 1:
The semiconductor spacer layer with optimized carrier concentration (10^19 to 10^21 carriers/cm³) provides balanced electrical and thermal properties. The material parameters are tuned to allow sufficient current flow for high output signal while the thermal conduction prevents excessive localized heating that would cause current migration, thus resolving the contradiction between operating current and reliability.
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
The solution significantly improves the magnetoresistive ratio and inhibits the increase in area resistivity, enabling the CPP-GMR element to be suitable for future high-density recording applications beyond 2 T bpsi.
Implementation Method 1
the spacer layer is formed on the first ferromagnetic layer under the condition of the epitaxial growth
Implementation Method 2
A magnetoresistive effect element (MR element) that is a giant magnetoresistive effect element in a current perpendicular to plane (CPP-GMR) structure
Data Source
AI summary
An MR element in a CPP-GMR structure includes a first ferromagnetic layer, a spacer layer that is epitaxially formed on the first ferromagnetic layer, a second ferromagnetic layer that is located on the spacer layer, and that is laminated with the first ferromagnetic layer to sandwich the spacer layer. A sense current flows along a lamination direction of the first and second ferromagnetic layers. Angle of magnetization directions of the first ferromagnetic layer and the second ferromagnetic layer relatively change due to an externally applied magnetic field.