Pd Underlayer Crystal Structure for Perpendicular Magnetic Recording
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Solution Overview
Problem
Existing perpendicular magnetic recording media face challenges in reducing grain size and improving crystal orientation, leading to limitations in recording density and reproduction characteristics due to the grain size of the nonmagnetic underlayer.
Innovation Solution
A perpendicular magnetic recording medium is developed with a first nonmagnetic underlayer having a fine crystal structure, made of Pd or a Pd alloy, which allows for the formation of finer crystal grains in the second nonmagnetic underlayer and perpendicular magnetic recording layer, improving orientation and recording/reproduction characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a crystalline seed layer with face-centered cubic structure is used to improve crystal orientation, then the crystal orientation of the recording layer is improved, but the grain size becomes difficult to downsize because the grain size of the seed layer is reflected on the nonmagnetic underlayer
Solution Approach 1:
The patent divides the nonmagnetic underlayer into two distinct layers: a first nonmagnetic underlayer with face-centered cubic structure for crystal orientation, and a second nonmagnetic underlayer with hexagonal closest packed structure for grain size control. This segmentation allows each layer to independently fulfill its specific function without compromising the other, resolving the contradiction between crystal orientation and grain size reduction.
Solution Approach 2:
The patent introduces a transition layer between the first nonmagnetic underlayer and the magnetic recording layer that has a specific crystal structure and orientation relationship. This intermediary layer acts as a mediator to decouple the grain size limitation from the magnetic recording layer, allowing the first nonmagnetic underlayer to provide crystal orientation while the second nonmagnetic underlayer controls grain size.
2Productivity
If the grain size in the first nonmagnetic underlayer is reduced to enable finer grains in the magnetic recording layer, then recording density can be increased, but the crystal orientation may be compromised
Solution Approach 1:
By segmenting the nonmagnetic underlayer into two functional layers with different crystal structures, the patent enables independent optimization: the first layer maintains crystal orientation for high-density recording while the second layer controls grain size for improved reproduction characteristics.
Solution Approach 2:
The patent applies different crystal structures and properties to different regions of the underlayer structure. The first nonmagnetic underlayer has face-centered cubic structure for crystal orientation, while the second nonmagnetic underlayer has hexagonal closest packed structure for grain size control, allowing each region to have the local quality needed for its specific function.
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 use of a fine crystal structured Pd or Pd alloy underlayer enables the creation of a high-density recording medium with improved crystallinity and recording/reproduction characteristics, surpassing conventional methods by allowing for smaller grain sizes and better orientation of the magnetic recording layer.
Implementation Method 1
a first nonmagnetic underlayer having a fine crystal structure and made of Pd or a Pd alloy, which allows for the formation of finer crystal grains in the second nonmagnetic underlayer and perpendicular magnetic recording layer
Data Source
AI summary
According to one embodiment, a soft magnetic layer, a first nonmagnetic underlayer having a fine crystal structure and made of Pd or a Pd alloy, a second nonmagnetic underlayer made of Ru or an Ru alloy, and a perpendicular magnetic recording layer are stacked on a nonmagnetic substrate.