Magnetic Recording Medium Exchange Coupling Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic recording systems face challenges in achieving high recording density while maintaining thermal stability and controlling temperature characteristics, particularly due to limitations in material properties and the inability to effectively reduce the reversing magnetic field during the writing process without compromising signal integrity.
Innovation Solution
A magnetic recording medium with a structure comprising two magnetic layers and an exchange coupling control layer, where the coupling energy is optimized to be weaker during writing and stronger during signal retention, using a nonmagnetic substance to surround magnetic crystal grains and employing a multilayered film structure with specific materials to manage saturation magnetization and crystalline anisotropy constants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the magnetization reversal unit size is reduced to increase recording density, then the cross sectional area decreases, but the thermal stability deteriorates due to decreased activation volume
Solution Approach 1:
The magnetic recording layer is divided into multiple magnetic layers (first magnetic layer and second magnetic layer) with different magnetization reversal characteristics. The first magnetic layer has higher crystalline magnetic anisotropy constant and higher Curie temperature, while the second magnetic layer has lower values. This segmentation allows the upper layer to provide thermal stability while the lower layer enables easier magnetization reversal during writing, resolving the contradiction between recording density and thermal stability.
2Reliability
If the crystalline magnetic anisotropy constant Ku is increased to improve thermal stability, then the reversing magnetic field increases, but the write performance deteriorates
Solution Approach 1:
Different regions of the magnetic recording layer are assigned different magnetic properties. The first magnetic layer (lower layer) is designed with higher Ku value to provide thermal stability, while the second magnetic layer (upper layer) is designed with lower Ku value to facilitate magnetization reversal during writing. This local differentiation of magnetic properties allows simultaneous optimization of both thermal stability and write performance.
Solution Approach 2:
The magnetic recording layer uses a composite structure of two different magnetic materials with distinct properties. The first magnetic layer uses a material with high crystalline magnetic anisotropy constant and high Curie temperature, while the second magnetic layer uses a material with lower values. This composite structure enables the system to exhibit both high thermal stability and ease of magnetization reversal depending on which layer is active.
3Ease of operation
If exchange coupling energy between magnetic layers is weakened to reduce reversing magnetic field, then write performance improves, but thermal stability may deteriorate
Solution Approach 1:
The exchange coupling energy between the first and second magnetic layers is precisely controlled by adjusting the thickness of the nonmagnetic substance layer separating them. By optimizing this parameter, the patent achieves weak enough coupling to reduce the reversing magnetic field for improved write performance, while maintaining sufficient coupling to preserve thermal stability. The different Curie temperatures of the two layers further modulate the effective coupling energy at operating temperatures.
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 approach allows for high-density recording by reducing the reversing magnetic field during writing while maintaining thermal stability and enabling effective temperature variation control, thereby enhancing recording density and signal integrity.
Implementation Method 1
an exchange coupling control layer inserted between the magnetic layers; the two magnetic layers being magnetically coupled through the exchange coupling control layer; a coupling energy in the process of writing a signal and a coupling energy in the state of retaining a signal being different from each other
Implementation Method 2
This method utilizes a characteristic of magnetic materials, a temperature dependence of the Ku, which decreases with increase in temperature. A write process in this method is conducted during temporary decrease in the Ku value attained by heating the magnetic recording layer
Implementation Method 3
a structure in which magnetic crystal grains are surrounded by a nonmagnetic substance
Data Source
AI summary
A magnetic recording medium for thermally assisted recording is disclosed which achieves both high density writing and good control of temperature characteristics. The magnetic recording medium for thermally assisted recording comprises an underlayer, a magnetic recording layer, and a protective layer sequentially laminated on a nonmagnetic substrate. The magnetic recording layer has a structure composed of two magnetic layers and an exchange coupling control layer inserted between the magnetic layers, the two magnetic layers being magnetically coupled through the exchange coupling control layer. The coupling energy Jw in the process of writing a signal and the coupling energy Jr in the state of retaining a signal satisfy a relation 0<Jw<Jr.