Magnetic Recording Medium LED Heating for Crystal Orientation
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Solution Overview
Problem
The high heating temperatures required for improving the crystal orientation of perpendicular magnetic layers in magnetic recording media adversely affect the underlayer, soft magnetic layer, and nonmagnetic substrate, leading to diffusion of elements, impaired soft magnetic properties, and surface undulations.
Innovation Solution
A magnetic recording medium manufacturing method that uses LED light with a center wavelength of less than 500 nm to heat the perpendicular magnetic layer, employing a multilayer underlayer structure with NaCl type compounds to prevent heat transfer to adjacent layers and substrate, ensuring uniform heating of the perpendicular magnetic layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the heating temperature of the perpendicular magnetic layer is increased to improve crystal orientation, then the crystal orientation of the perpendicular magnetic layer is improved, but the heat affects the underlayer, soft magnetic layer, and nonmagnetic substrate, causing element diffusion, impaired soft magnetic properties, and surface undulations
Solution Approach 1:
The underlayer is divided into multiple segments with different functions: a first underlayer (Ta or W) that reflects light and prevents heat from reaching the soft magnetic layer, a second underlayer (MgO with NaCl structure) that provides (001) orientation to the perpendicular magnetic layer, and a third underlayer (Cr or Cr alloy) that ensures stable (100) orientation. This segmentation allows each layer to perform its specific function while preventing harmful heat transfer to other layers.
Solution Approach 2:
The first underlayer made of Ta or W acts as an intermediary between the LED light source and the soft magnetic layer. It reflects the LED light (wavelength 405-480 nm) back upward, preventing the light energy from being absorbed by the soft magnetic layer and causing unwanted heating. This intermediary layer protects the soft magnetic layer while allowing the perpendicular magnetic layer to receive sufficient heat for crystal orientation improvement.
2Temperature
If conventional heating methods are used to heat the perpendicular magnetic layer, then the heating temperature can be increased, but the heating affects the entire structure including the substrate, causing strain relaxation and crystal enlargement in the nonmagnetic substrate
Solution Approach 1:
The heating is localized to only the perpendicular magnetic layer through the use of LED light with wavelength 405-480 nm that is absorbed by the perpendicular magnetic layer but reflected by the first underlayer. This creates a local heating effect where only the intended layer is heated to the required temperature, while other layers remain at lower temperatures, preventing substrate strain relaxation and maintaining structural integrity.
3Manufacturing precision
If the heating temperature is increased to achieve L10 ordering in FePt alloys, then the magnetic anisotropy is improved, but the soft magnetic layer becomes crystallized and loses its soft magnetic properties
Solution Approach 1:
The first underlayer (Ta or W) serves as a thermal barrier and light reflector that prevents heat from reaching the soft magnetic layer. By reflecting LED light upward and blocking thermal conduction, it ensures that the soft magnetic layer remains below its crystallization temperature while the perpendicular magnetic layer reaches the required temperature for L10 ordering, thus preserving the amorphous structure and soft magnetic properties of the soft magnetic layer.
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 method effectively enhances crystal orientation of the perpendicular magnetic layer while preventing heat-induced damage to other layers and the substrate, maintaining the integrity and electromagnetic conversion characteristics of the magnetic recording medium.
Implementation Method 1
heating a surface of the perpendicular magnetic layer by LED light emitted from a LED light source after forming the perpendicular magnetic layer, to improve a crystal orientation of the perpendicular magnetic layer
Implementation Method 2
the underlayer includes a NaCl type compound... preventing the heat during the heating of the perpendicular magnetic layer from affecting other layers and the substrate
Implementation Method 3
it is known that a heat treatment at a high temperature of 400° C. or higher is required for the L10 ordering of the FePt alloys
Implementation Method 4
FePt alloys having a L10 ordered structure... improve a crystal orientation of the perpendicular magnetic layer
Data Source
AI summary
A magnetic recording medium manufacturing method for manufacturing a magnetic recording medium having a substrate, an underlayer, and a perpendicular magnetic layer having a L10 structure in this order, includes heating a surface of the perpendicular magnetic layer by LED light emitted from a LED light source after forming the perpendicular magnetic layer, to improve a crystal orientation of the perpendicular magnetic layer, wherein the underlayer includes a NaCl type compound, and the LED light has a center wavelength of less than 500 nm.