Perpendicular Magnetic Recording Medium Ru Intermediate Layer
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Solution Overview
Problem
Existing perpendicular magnetic recording technologies face challenges in achieving high recording density while maintaining low noise levels, particularly due to noise generated from the interface with the intermediate layer in hard disk devices, which affects the magnetic anisotropy and stability of the recording signal.
Innovation Solution
A perpendicular magnetic recording medium is developed with a granular structure comprising a ruthenium or ruthenium alloy intermediate layer and cobalt-chromium alloy recording layers, where the first recording layer has a lower saturation magnetization than the second layer, and the film thickness and chromium content are optimized to reduce noise and improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a granular recording layer with oxygen or oxides added to CoCrPt alloy is used, then noise is reduced by magnetically isolating magnetic grains, but chromium content within magnetic grains increases causing magnetic anisotropy energy to drop and recording signal stability to deteriorate
Solution Approach 1:
An intermediate layer made of ruthenium or ruthenium alloy is introduced between the soft magnetic layer and the granular recording layer. This intermediate layer serves as a mediator that enables the formation of oxide grain boundaries in the recording layer without requiring excessive chromium content, thus reducing noise while maintaining magnetic anisotropy energy and recording signal stability.
Solution Approach 2:
The invention optimizes the chromium content in the granular recording layer to be 5-15 atomic percent, which is lower than conventional formulations. By changing this compositional parameter and combining it with the intermediate layer, the invention achieves noise reduction through oxide grain boundaries while preventing the drop in magnetic anisotropy energy that would otherwise occur with lower chromium content.
2Object-generated harmful factors
If large amounts of chromium are added to increase noise reduction effect, then noise is reduced, but magnetic anisotropy energy drops and stability of recording signal deteriorates
Solution Approach 1:
The ruthenium or ruthenium alloy intermediate layer acts as a mediator that enables effective noise reduction through oxide grain boundary formation without requiring large amounts of chromium. This allows the system to achieve noise reduction while maintaining sufficient chromium content (5-15 atomic percent) to preserve magnetic anisotropy energy and recording signal stability.
3Stability of the object's composition
If conventional under layer materials such as CoCr alloy or titanium alloy are used, then c-axis orientation is obtained, but oxide grain boundary formation is insufficient and noise reduction effect is inadequate
Solution Approach 1:
The invention changes the material composition of the intermediate layer from conventional CoCr alloy or titanium alloy to ruthenium or ruthenium alloy. This compositional change enables effective oxide grain boundary formation in the recording layer, achieving noise reduction while still maintaining the necessary c-axis orientation through the hexagonal closed packed structure of ruthenium that matches CoCrPt alloy.
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 significantly enhances the signal-to-noise ratio and achieves high recording density, enabling a reliable and durable magnetic storage device capable of withstanding long-term use with improved overwrite characteristics.
Implementation Method 1
Ruthenium grains possess a hexagonal closed packed structure identical to CoCrPt alloy so that the CoCrPt alloy can grow epitaxially on the ruthenium (Ru) layer and obtain a satisfactory c-axis orientation
Implementation Method 2
the noise was reduced by magnetically isolating the magnetic grains, by segregating the non-magnetic material into grain boundaries mainly of chromium by utilizing the cobalt and chromium phase separation
Implementation Method 3
the perpendicular magnetic recording method is better for high density information storage... the high density recording region is less susceptible to effects from demagnetizing fields
Data Source
AI summary
Embodiments in accordance with the present invention provide a perpendicular recording medium with low noise and high recording density by reducing the effects from noise generated from the vicinity of the interface with the intermediate layer of the recording layer, in a perpendicular recording medium utilizing a granular recording layer containing oxygen or oxide additive in a cobalt-chromium alloy formed on an intermediate layer with a ruthenium or ruthenium alloy layer. A first recording layer and a second recording layer are formed in order on an intermediate layer of ruthenium or ruthenium alloy. The first recording layer and the second recording layer are comprised of cobalt as the main material in a granular structure containing chromium and oxygen. The saturation magnetization of the first recording layer is lower than the saturation magnetization of the second recording layer. When a first recording layer saturation magnetization is set as Ms1(emu per cubic centimeter), a second recording layer saturation magnetization is set as Ms2(emu per cubic centimeter), and the first recording layer film thickness is set to t1 (nm), then (Ms2−Ms1)×t1 will be larger than 0 (memu per square centimeter) and smaller than 0.15 (memu per square centimeter).