Dual NiFe Seed Layer for Magnetic Recording Media Grain Texture
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Solution Overview
Problem
Existing magnetic recording media designs face a challenge in achieving both small grain size and good crystallographic texture, as these goals are often in conflict with each other, with thin seed layers providing small grain size but poor texture, and thick seed layers providing good texture but large grain size.
Innovation Solution
A dual seed layer with a graded composition is used, comprising a first seed layer of NiFe at a specific concentration and a second seed layer of NiFe at a different concentration with a segregant, such as oxides or increased concentrations of elements like W and Al, to achieve small grain size and good crystallographic texture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a thin seed layer is used, then small grain size is achieved, but crystallographic texture deteriorates
Solution Approach 1:
The seed layer is divided into two distinct layers: a first seed layer (5-15 nm thick) that provides small grain size, and a second seed layer (15-30 nm thick) that provides good crystallographic texture. This segmentation allows each layer to independently fulfill its specific function without compromising the other, resolving the contradiction between grain size and texture quality.
Solution Approach 2:
Each seed layer is given different local properties: the first seed layer has composition optimized for grain size control, while the second seed layer has composition optimized for crystallographic texture. The second layer contains higher Ni content (65-75 at%) compared to the first layer (55-65 at% Ni), creating local quality differences that enable simultaneous achievement of small grains and good texture.
2Manufacturing precision
If a thick seed layer is used, then good crystallographic texture is achieved, but grain size increases
Solution Approach 1:
The thick seed layer is segmented into two functional layers. The second seed layer (thicker, 15-30 nm) provides the crystallographic texture through its composition and thickness, while the first seed layer (thinner, 5-15 nm) controls the grain size. This segmentation prevents the grain size increase that would normally accompany a thick single layer.
Solution Approach 2:
The dual seed layer structure creates a composite material system where two layers with different compositions (NiFe ratios) work together. The first layer (55-65 at% Ni) and second layer (65-75 at% Ni) form a composite that achieves properties neither layer could provide alone, specifically simultaneous small grain size and good crystallographic texture.
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 dual seed layer design enhances the media's signal-to-noise ratio and areal density capacity by maintaining a narrow X-ray rocking angle and reducing grain size and center-to-center distance, while maintaining good crystallographic texture, thereby improving recording performance.
Implementation Method 1
a dual seed layer that includes a first seed layer comprising NiFe at a first concentration, and a second seed layer comprising NiFe at a second concentration different from the first concentration
Implementation Method 2
a second seed layer comprising NiFe at a second concentration different from the first concentration and a segregant
Implementation Method 3
good crystallographic texture
Implementation Method 4
narrow X-ray rocking angle
Data Source
AI summary
A magnetic recording medium includes a substrate, a soft magnetic underlayer on the substrate, and a dual seed layer. The dual seed layer includes a first seed layer comprising NiFe at a first concentration, and a second seed layer comprising NiFe at a second concentration different from the first concentration and a segregant. The first seed layer may be on a soft magnetic underlayer and the second seed layer is on the first seed layer. The magnetic recording medium may further include one or more magnetic recording layers on the dual seed layer. The magnetic recording medium with the composition-graded dual seed layer may provide small grain size and good crystallographic texture for layers on the dual seed layer, including the magnetic recording layers.