Soft Magnetic Underlayer Temperature Robustness
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Solution Overview
Problem
Current soft magnetic underlayers (SULs) in perpendicular magnetic recording media experience a significant decrease in magnetic flux density at higher temperatures, leading to degraded writeability, which limits their use in high-temperature conditions such as vehicle storage systems.
Innovation Solution
A soft magnetic underlayer structure with a coupling layer and two antiferromagnetically coupled soft underlayers, where the difference in magnetic flux density between 25°C and 85°C is less than or equal to 10% of the flux density at 25°C, is implemented to maintain writeability across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the saturation magnetic flux density (Bs) of the SUL is decreased to improve writeability in perpendicular magnetic recording media, then the magnetic permeability increases and writeability improves, but the Bs decreases at a higher rate with increasing temperature, leading to degraded writeability at high temperature
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition of the soft magnetic underlayer, specifically adjusting the ratios of Co, Fe, and alloying elements (Ta, W, Mo, Nb, Hf) to achieve an optimal balance between low Bs at room temperature for improved writeability and sufficient Bs at high temperature for stability. The controlled composition parameters enable the SUL to maintain adequate magnetic flux density across temperature variations while preserving enhanced writeability characteristics
Solution Approach 2:
The patent employs composite materials by creating a multi-element alloy system combining Co-Fe base metals with specific amounts of alloying elements (Ta: 1-15 at.%, W: 1-15 at.%, Mo: 1-15 at.%, Nb: 1-15 at.%, Hf: 1-15 at.%). This composite approach leverages the synergistic effects of different elements to achieve both low room-temperature Bs for improved writeability and high-temperature Bs stability, resolving the contradiction between immediate performance and thermal robustness
2Area of moving object
If the width of the poles on the read/write head is narrowed to increase track density, then the number of tracks that can be written increases, but the strength of the head's write field decreases, resulting in degradation of writeability
Solution Approach 1:
The patent applies parameter changes by optimizing the SUL's magnetic parameters (Bs and permeability) through compositional control. By adjusting the Co-Fe ratio and alloying element concentrations, the SUL achieves low Bs at room temperature which increases magnetic permeability, thereby enhancing writeability and compensating for the reduced write field strength caused by narrower head poles
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 solution effectively suppresses the decrease in magnetic flux density with increasing temperature, ensuring consistent writeability and improving the performance of perpendicular magnetic recording media in high-temperature environments.
Implementation Method 1
a soft magnetic underlayer structure with a coupling layer and two antiferromagnetically coupled soft underlayers
Data Source
AI summary
In one embodiment, a perpendicular magnetic recording medium includes: a substrate; and a soft magnetic underlayer structure positioned above the substrate, where the soft magnetic underlayer includes: a coupling layer; a first soft underlayer positioned above the coupling layer; and a second soft underlayer positioned below the coupling layer, where a difference between a magnetic flux density of the soft magnetic underlayer structure at 25° C. and a magnetic flux density of the soft underlayer structure at 85° C. is less than or equal to about 10% of the magnetic flux density of the soft magnetic underlayer structure at 25° C.