CoPtCr Bit-Patterned Magnetic Media for High Density Storage
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Solution Overview
Problem
Conventional magnetic disk storage media face limitations in achieving high areal recording density due to the superparamagnetic effect, which causes instability in magnetization as grain size decreases, leading to loss of stored information and noise generation.
Innovation Solution
The development of bit-patterned magnetic media with a substrate and discrete magnetic elements formed from a stack of thin film layers, including a seed layer and a perpendicular magnetic recording layer made of Co1-x-yPtxCry alloy, which provides high magnetic anisotropy and saturation magnetization, allowing for stable magnetization and increased areal recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If grain size of magnetic film is decreased to increase areal recording density, then storage capacity is improved, but magnetization stability deteriorates due to superparamagnetic effect
Solution Approach 1:
The continuous magnetic film is divided into discrete magnetic islands or grains separated by non-magnetic material. This segmentation isolates each magnetic grain, preventing thermal fluctuations from affecting the entire film and stabilizing magnetization at high areal densities.
Solution Approach 2:
The patent uses composite magnetic layer structures including CoCrPt alloys with specific compositions and thicknesses, combined with non-magnetic underlayers and overlayers. This composite structure provides both high magnetization for storage capacity and sufficient anisotropy energy for thermal stability.
2Force
If saturation magnetization and film thickness are increased to obtain sufficient output signal from minute bits, then signal strength is improved, but superparamagnetic effect worsens due to increased thermal fluctuation impact
Solution Approach 1:
The patent optimizes multiple parameters including CoCrPt alloy composition (Co: 65-75 at%, Cr: 15-30 at%, Pt: 5-20 at%), layer thicknesses (magnetic layer: 3-10 nm, underlayer: 5-20 nm), and crystalline structure to achieve the desired balance between signal strength and thermal stability.
Solution Approach 2:
Different layers in the magnetic recording medium have different compositions and properties optimized for their specific functions: the CoCrPt magnetic layer for high magnetization, the non-magnetic underlayer for spin polarization, and the overlayer for protection. Each layer's local properties are tailored to contribute to overall performance.
3Quantity of substance
If magnetic grain size is reduced to achieve higher areal recording density, then storage capacity is improved, but noise generation increases due to ragged boundaries between adjacent bits
Solution Approach 1:
By segmenting the magnetic film into discrete, well-defined grains separated by non-magnetic material, the patent creates clear boundaries between adjacent bits. This eliminates the ragged boundaries in continuous films that cause noise during reading, while maintaining high areal recording density through optimized grain size and spacing.
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 enables areal recording densities ranging from 250 Gbit/in2 to 10 Tbit/in2, reducing noise and errors, and enhancing magnetic performance and stability, thus overcoming the limitations of conventional continuous magnetic media.
Implementation Method 1
comprising a Co1-x-yPtxCry alloy material, where 0.05≦x≦0.35 and 0≦y≦0.15
Implementation Method 2
the requirement for increased areal recording density has necessitated a corresponding decrease in recording bit size or area. Consequently, grain sizes of continuous film media have become extremely minute, e.g., on the order of nanometers (nm). In order to obtain a sufficient output signal from such minute bits, the saturation magnetization (Ms) and thickness of the film must be as large as possible. However, the magnetization of such minute bits is extremely small, resulting in a loss of stored information due to magnetization reversal by 'thermal fluctuation', also known as the 'superparamagnetic effect'.
Implementation Method 3
for perpendicular type continuous magnetic media, wherein the magnetic easy axis is oriented perpendicular to the film plane (i.e., surface), growth of the magnetic particles or grains in the film thickness direction increases the volume of magnetization of the particles or grains while maintaining a small cross-sectional area (as measured in the film plane). As a consequence, onset of the superparamagnetic effect can be suppressed for very small particles or grains of minute width.
Data Source
AI summary
A bit patterned magnetic recording medium comprises a substrate having a surface, and a plurality of spaced apart magnetic elements on the surface, each element constituting a discrete magnetic domain or bit of the same structure and comprised of a stack of thin film layers including in order from the substrate surface: a seed layer; and a perpendicular magnetic recording layer in contact with a surface of the seed layer and comprising a Co 1-x-yPtxCry alloy material, where 0.05≦x≦0.35 and 0≦y≦0.15. The Co1-x-yPtxCry alloy material has a first order magnetic anisotropy constant K1 up to about 2×107 erg/cm3, a saturation magnetization Ms up to about 1200 emu/cm3, an anisotropy field HK=2K1/Ms up to about 35 kOe, a hexagonal (0001) crystal structure with c-axis perpendicular to a surface thereof, and an X-Ray diffraction (XRD) rocking curve with a full width at half maximum (FWHM) of ˜5° or less.