CoFe CPP Magnetoresistive Element with fcc-hcp Interface
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Solution Overview
Problem
Current CPP-type magnetoresistive effect elements face challenges in achieving a high MR ratio while maintaining low resistance, essential for increasing recording density in magnetic disk drives, due to limitations in the crystal structures of CoFe magnetic layers and spacer layers.
Innovation Solution
The development of a CPP-GMR element with a spacer layer made of nonmagnetic materials like GaN and CoFe magnetic layers with a face-centered cubic (fcc) and hexagonal closed-packed (hcp) crystal structures at the interface, where at least one of the CoFe system magnetic alloys contains 25% or more Fe by atomic weight, enhancing the MR ratio through improved atomic packing and symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CoFe magnetic layers with bcc crystal structure are used, then the element resistance is low, but the MR ratio is insufficient for high recording density
Solution Approach 1:
The patent changes the crystal structure parameter of the CoFe magnetic layer from conventional bcc to fcc or hcp structures by controlling the spacer layer material and deposition conditions. This parameter change increases the MR ratio while maintaining low resistance, directly resolving the contradiction between measurement precision and reliability
Solution Approach 2:
The patent creates a composite structure combining CoFe magnetic layers with specific crystal structures (fcc or hcp) and nonmagnetic spacer layers (Ru, Rh, Ir). This composite material approach enhances the MR ratio through improved atomic packing and symmetry at the interface, while the overall structure maintains low resistance for high signal-to-noise ratio
2Productivity
If the cross sectional area of the element is reduced to increase TPI, then the number of tracks per inch increases, but the resistance value increases and MR ratio varies more
Solution Approach 1:
By changing the crystal structure parameter to fcc or hcp, the patent achieves more stable resistance values and MR ratios even in narrower track widths. The improved atomic packing density and interface symmetry compensate for the reduced cross-sectional area, enabling higher TPI with controlled resistance
3Measurement precision
If Fe content in CoFe alloy is increased to improve MR ratio, then the MR ratio tends to be higher, but the crystal structure stability may be affected
Solution Approach 1:
The patent optimizes the Fe content parameter in the CoFe alloy to achieve the desired MR ratio while maintaining crystal structure stability. By controlling the Fe concentration and combining it with specific spacer layer materials, the patent stabilizes the fcc or hcp crystal structure even with higher Fe content, resolving the contradiction between measurement precision and composition stability
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 significantly increases the MR ratio, leading to improved signal-to-noise ratios and higher recording densities in magnetic disk drives, as demonstrated by experiments showing high MR ratios when the fcc and hcp structures occupy 25% or more of the interface area.
Implementation Method 1
giant magnetoresistive effect element in a current perpendicular to plane (CPP-GMR) structure
Data Source
AI summary
In an MR element of the present invention, an effect of an extremely-high MR ratio is obtained since a crystal structure of a CoFe magnetic layer in the vicinity of an interface with a spacer layer is formed as a close packed structure, such as an hcp structure and an fcc structure, and a total existing ratio of these crystal structures is 25% or more by an area ratio.