Seed Layer Design for FePt Perpendicular Magnetic Recording Media
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Solution Overview
Problem
Current magnetic recording technologies face challenges in achieving high data density and thermal stability, particularly at elevated temperatures, due to unstable magnetic signals and poor crystal orientation in FePt layers, which affects the signal-to-noise ratio and reverses magnetic field dispersion.
Innovation Solution
A magnetic medium with a seed layer comprising elements like Cr, Co, Fe, Ni, W, Mo, or Ru is used, along with a MgO under-layer and an FePt recording layer with an L10-type crystal structure, to improve crystal orientation and reduce dispersion, enhancing the signal-to-noise ratio and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If magnetic data density is increased, then recording capacity is improved, but magnetic signal stability deteriorates at elevated temperatures
Solution Approach 1:
The patent applies parameter changes by heating the magnetic medium to an elevated temperature during the writing process. This temporary temperature increase modifies the magnetic properties of the recording layer, reducing its coercivity and allowing magnetization to be aligned by the write field. After writing, the medium cools down, restoring high coercivity and thermal stability for data retention.
Solution Approach 2:
The patent utilizes phase transitions in the magnetic recording layer by exploiting the temperature-dependent magnetic phase behavior. At elevated temperatures, the magnetic layer transitions to a state with lower anisotropy and coercivity, enabling easy magnetization switching. Upon cooling, it transitions back to a high-coercivity state that provides thermal stability for stored data.
2Ease of manufacture
If FePt layer crystal orientation is poor, then manufacturing is easier, but signal-to-noise ratio deteriorates and magnetic field dispersion increases
Solution Approach 1:
The patent introduces a seed layer as an intermediary between the substrate and the FePt recording layer. This seed layer, composed of specific materials and structures, mediates the crystal growth of the FePt layer, promoting the formation of the desired L10-type crystal structure with proper orientation. The seed layer makes the manufacturing process feasible while ensuring high signal-to-noise ratio by achieving proper crystal orientation.
Solution Approach 2:
The patent employs composite material structure by combining the seed layer with the FePt recording layer in a specific configuration. The seed layer materials (which may include various metallic or alloy components) work synergistically with the FePt layer to achieve both manufacturability and high performance, creating a composite structure that addresses both ease of manufacture and signal quality requirements.
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 proposed solution improves crystal orientation and reduces magnetic field dispersion, resulting in increased signal-to-noise ratio and thermal stability, enabling high-density and thermally stable magnetic recording.
Implementation Method 1
a magnetic medium with a seed layer comprising elements like Cr, Co, Fe, Ni, W, Mo, or Ru is used, along with a MgO under-layer and an FePt recording layer with an L10-type crystal structure, to improve crystal orientation
Implementation Method 2
magnetic recording layer with a high magnetic anisotropy Ku in a direction perpendicular to the plane of the surface of the media
Implementation Method 3
the magnetic media is locally heated at the time of writing. This temporarily lowers the coercivity of the magnetic recording layer to allow the magnetization of the magnetic recording layer to be aligned by a magnetic write field
Implementation Method 4
An electrically conductive write coil is wrapped around the write pole and induces a magnetic flux that magnetizes the write pole when a current is passed through the coil
Implementation Method 5
A magnetoresistive sensor such as a GMR or TMR sensor can be employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, or barrier layer, sandwiched between first and second ferromagnetic layers
Data Source
AI summary
A magnetic medium for perpendicular magnetic data recording, having improved magnetic properties through use of a novel seed layer. The magnetic medium includes a substrate having a seed layer, a magnetic under-layer and a magnetic recording layer formed there-over. The seed layer includes an element selected from a first group of Cr, Co, Fe and Ni, and at least one element that is selected from the other elements of the first group or from a second group consisting of W, Mo and Ru. A buffer layer may be included between the substrate and the seed layer.