NiW Alloy Under Layer for Perpendicular Magnetic Recording Medium
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Solution Overview
Problem
Conventional perpendicular magnetic recording media face challenges in maintaining excellent overwrite (OW) properties due to decreased magnetic coupling between the magnetic head and the soft magnetic backing layer, primarily because the under layer's thickness affects magnetic coupling, and materials like 94Ni6W alloy have insufficient saturation magnetic flux density, limiting the control over the generation of nuclei for the intermediate Ru layer.
Innovation Solution
A perpendicular magnetic recording medium is developed with a soft magnetic film backing layer and an under layer containing NiW alloy with W content between 3 to 10 atom % and Co or Fe content of 5 to 40 atom %, achieving a saturation magnetic flux density of 280 emu/cm3 or more, while maintaining the control over the generation of nuclei for the Ru intermediate layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the under layer is increased to control the generation of nuclei for the intermediate Ru layer, then the control over nuclei generation is improved, but magnetic coupling between the magnetic head and the soft magnetic backing layer is decreased, resulting in deteriorated OW properties
Solution Approach 1:
The invention changes the material composition parameters of the under layer by introducing Co or Fe into the NiW alloy, adjusting the saturation magnetic flux density to 280 emu/cm³ or more while maintaining the thickness between 2 to 20 nm. This parameter change enables simultaneous achievement of good OW properties and control over nuclei generation.
2Length of moving object
If 94Ni6W alloy is used in the under layer to maintain a thin under layer, then the OW properties are improved, but the saturation magnetic flux density is only about 250 emu/cm³, which is not enough to increase magnetic coupling
Solution Approach 1:
The invention uses a composite alloy material consisting of Ni, W, Co, and Fe in the under layer. By combining these materials with specific composition ratios (W: 3-10 atom %, Co+Fe: 5-40 atom%), the saturation magnetic flux density is increased to 280 emu/cm³ or more while maintaining the thin under layer thickness, thus improving magnetic coupling without increasing thickness.
3Reliability
If the W content of NiW alloy is decreased to increase saturation magnetic flux density, then magnetic coupling is improved, but the function of controlling the generation of nuclei for the intermediate Ru layer decreases
Solution Approach 1:
The invention optimizes the W content parameter to 3-10 atom % and introduces Co or Fe at 5-40 atom % to achieve a balance. This parameter optimization maintains the saturation magnetic flux density at 280 emu/cm³ or more for good magnetic coupling while preserving the under layer's ability to control nuclei generation for the intermediate Ru layer.
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 enhances the saturation magnetic flux density and maintains the control over the intermediate layer's nuclei generation, resulting in improved OW properties and recording/reproducing performance.
Implementation Method 1
magnetic coupling between the magnetic head and the soft magnetic backing layer
Implementation Method 2
saturation magnetic flux density (Bs) of only about 250 emu/cm3
Data Source
AI summary
A perpendicular magnetic recording medium of the present invention comprises a non-magnetic substrate, and at least a backing layer, an under layer, an intermediate layer and a perpendicular magnetic recording layer, which are sequentially laminated on the non-magnetic substrate, wherein the backing layer is formed of a soft magnetic film having an amorphous structure, the under layer contains a NiW alloy containing any one or both of Co and Fe, the W content of the NiW alloy is within a range from 3 to 10 atom %, the total of the Co and Fe contents of the NiW alloy is 5 atom % or more and less than 40 atom %, the saturation magnetic flux density Bs of the NiW alloy is 280 emu/cm3 or more, the thickness of the under layer is within a range from 2 to 20 nm, and the intermediate layer contains Ru or a Ru alloy.