Perpendicular Magnetic Disk Amorphous Alloy Layer Crystal Orientation
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Solution Overview
Problem
To further increase recording density in perpendicular magnetic disks, it is necessary to improve the crystal orientation of the magnetic particles and the ground layer, which is essential for enhancing the Signal to Noise Ratio (SNR).
Innovation Solution
A perpendicular magnetic disk structure is implemented with an amorphous alloy layer containing Ta, a preliminary ground layer formed of Ti microcrystals, and a second preliminary ground layer with an fcc crystal structure, which improves the crystal orientation and flatness, leading to enhanced SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the film thickness is increased to improve crystal orientation, then crystal orientation improves, but the structure becomes more complex and manufacturing becomes more difficult
Solution Approach 1:
The preliminary ground layer is divided into two distinct layers: a first preliminary ground layer (5-15 nm thick) and a second preliminary ground layer (2-10 nm thick). This segmentation allows each layer to perform its specific function - the first layer provides initial crystal nucleation sites while the second layer enhances crystal orientation - thereby achieving excellent crystal orientation without requiring excessive total thickness
Solution Approach 2:
Different materials are used for different layers to optimize local properties. The first preliminary ground layer uses Ti or Ti alloy (hcp structure) to provide initial crystal nuclei, while the second preliminary ground layer uses Ni-type alloy (fcc structure) to enhance crystal orientation. This local differentiation of material properties enables superior overall crystal orientation with controlled thickness
2Reliability
If multiple preliminary ground layers are added to improve crystal orientation, then SNR improves, but device complexity increases
Solution Approach 1:
The preliminary ground layer is segmented into two functional layers with distinct thicknesses and materials. The first layer (5-15 nm) provides initial crystal nucleation, while the second layer (2-10 nm) enhances crystal orientation. This segmentation achieves superior SNR through improved crystal orientation without creating excessive structural complexity
Solution Approach 2:
By changing the material composition (Ti/Ti alloy for first layer, Ni-type alloy for second layer) and controlling thickness parameters (5-15 nm and 2-10 nm respectively), the patent optimizes crystal orientation to improve SNR while maintaining manageable device complexity
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 improved crystal orientation and flatness achieved by this structure result in increased recording density and SNR, with the amorphous alloy layer and microcrystalline Ti layers ensuring a fine structure and flat surface, while the fcc crystal structure enhances the SNR.
Implementation Method 1
When a metal film of an hcp structure is formed by sputtering
Implementation Method 2
a crystalline preliminary ground layer (also called a seed layer) is provided below the Ru ground layer to improve the crystal orientation of the Ru ground layer
Implementation Method 3
Co has an hcp structure (a hexagonal close-packed structure), and a c-axis direction (an axial direction of a hexagonal column of a crystal grating) serves as an easy axis of magnetization. Therefore, by orienting the c axis of more crystals in a more perpendicular direction, noise is reduced and also a signal is strengthened
Data Source
AI summary
A perpendicular magnetic disk that includes, on a base, a soft magnetic layer, an amorphous alloy layer, a preliminary ground layer provided on the amorphous alloy layer, a ground layer formed of Ru or a Ru-type alloy having an hcp crystal structure provided on the preliminary ground layer. A granular magnetic layer is provided on the ground layer. The amorphous alloy layer contains Ta, and the preliminary ground layer includes a first preliminary ground layer formed of Ti or a Ti alloy of microcrystals and a second preliminary ground layer formed of a Ni-type alloy of an fcc crystal structure.