Granular Ru Underlayer for Perpendicular Magnetic Recording Noise Reduction
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Solution Overview
Problem
In perpendicular magnetic recording media, the formation of Ru layers under the recording layer leads to crystallization of magnetic particles, causing them to combine and resulting in insufficient isolation, increased noise, and spread in particle diameter, which affects recording density and data integrity.
Innovation Solution
A perpendicular magnetic recording medium is developed with a substrate, a soft-magnetic underlayer, a seed layer from amorphous material, an underlayer of Ru or Ru alloy with granular crystals growing perpendicular to the substrate and separated by interstices, and a recording layer with magnetic particles having an easy axis perpendicular to the substrate, along with non-magnetic immiscible phases for improved isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a Ru layer is formed under the recording layer to control magnetic particle growth, then magnetic particle isolation is improved, but magnetic particles combine and form irregular distributions increasing noise
Solution Approach 1:
A non-magnetic underlayer comprising granular crystals and interstices is introduced as an intermediary between the Ru layer and the recording layer. This non-magnetic underlayer acts as a mediator that prevents direct contact and combination of magnetic particles while maintaining controlled isolation, thereby reducing noise generated by irregular particle distributions
Solution Approach 2:
The underlayer structure is designed as a composite material system combining Ru granular crystals with non-magnetic phases forming interstices. This composite structure provides both the magnetic particle isolation benefits of granular crystals and the noise reduction capabilities of non-magnetic separation phases
2Ease of manufacture
If heating temperature is increased to form CoCr-based alloy recording layer, then recording layer formation is improved, but soft magnetic underlayer crystallizes causing spike noises
Solution Approach 1:
The soft magnetic underlayer is designed with specific compositional parameters (containing B, Si, or C elements) and thickness parameters (5-20 nm) that enable it to remain amorphous or micro-granular even when heated to high temperatures during recording layer formation, thus preventing crystallization and spike noise generation
Solution Approach 2:
The soft magnetic underlayer is designed as a thin, sacrificial layer that can be heated to high temperatures without permanent damage or crystallization. It serves its purpose during recording layer formation and maintains its noise-reducing properties throughout the device lifecycle
3Manufacturing precision
If magnetic particle size is reduced to increase recording density, then recording resolution is improved, but noise increases due to insufficient isolation
Solution Approach 1:
The underlayer is segmented into granular crystals separated by interstices, creating a periodic structure that provides consistent isolation for each magnetic particle. This segmentation ensures that even as particle size decreases, each particle maintains adequate isolation, preventing noise while enabling higher recording density
Solution Approach 2:
The non-magnetic underlayer is designed with a porous structure comprising granular crystals and interstices. This porous architecture provides physical separation and magnetic isolation for miniaturized magnetic particles, enabling high recording density without the noise that would normally accompany reduced particle isolation
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 reduces noise, improves magnetic particle distribution, and increases recording density by ensuring uniform growth of granular crystals and magnetic particles, enhancing data storage capacity and integrity.
Implementation Method 1
a seed layer formed from an amorphous material on the soft-magnetic underlayer; an underlayer formed from Ru or a Ru alloy on the seed layer. The underlayer includes a plurality of granular crystals each growing in a direction perpendicular to a surface of the substrate
Implementation Method 2
The recording layer is usually formed from a CoCr-based alloy, and is applied on the substrate by sputtering the CoCr-based alloy onto the substrate
Implementation Method 3
a recording layer on the underlayer. The recording layer includes a plurality of magnetic particles each having an easy axis of magnetization substantially perpendicular to a surface of the substrate, and a plurality of non-magnetic immiscible phases separating the magnetic particles from each other
Data Source
AI summary
A perpendicular magnetic recording medium is disclosed that includes a recording layer having a columnar granular structure possessing an appropriate diameter distribution and uniform arrangement of magnetic particles. The perpendicular magnetic recording medium includes a substrate, and a soft-magnetic underlayer, a seed layer, an underlayer, a recording layer, a protection film, and a lubrication layer stacked on the substrate in order. The underlayer includes granular crystals formed from Ru or a Ru alloy and interstices separating the granular crystals from each other so as to isolate individual granular crystals. A continuing film formed from Ru or Ru alloys may be provided below the underlayer.