Thermal-Assisted Magnetic Recording Density Control
Solution Overview
Problem
Conventional magnetic recording media face challenges in achieving high-density recording with stable thermal stability and reliability due to issues with magnetic domain wall movement and coercive force, especially when using thermally-assisted methods, which can lead to instability and interference between adjacent marks.
Innovation Solution
A method for recording and reproducing from a magnetic recording medium that controls the temperature distribution during recording and reproduction by varying parameters such as light wavelength, numerical aperture, and spot diameter, using different light sources and waveguides for recording and reproduction, and adjusting the temperature gradient to optimize domain wall movement and signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thermally-assisted recording is used to achieve high-density recording, then recording density is improved, but thermal stability and reliability of recorded magnetic domains deteriorate
Solution Approach 1:
The patent applies local quality by creating different temperature distributions in different regions of the magnetic recording medium. During recording, a first temperature distribution is applied to facilitate domain wall movement and recording, while during reproduction, a second temperature distribution is applied to enhance signal detection. This localized temperature control allows high-density recording while maintaining thermal stability of the recorded domains.
Solution Approach 2:
The patent employs dynamics by making the temperature distribution time-dependent and process-specific. The temperature distribution is not static but is dynamically adjusted according to whether the medium is being recorded from or reproduced from. This dynamic temperature control enables the system to optimize for recording density during writing and for thermal stability during reading.
2Quantity of substance
If laser irradiation is used to raise temperature for recording, then coercive force is reduced enabling high-density recording, but domain wall movement becomes unstable
Solution Approach 1:
The patent applies local quality by spatially separating the heating regions during recording and reproduction. During recording, the laser irradiates a first region to create a first temperature distribution that facilitates domain wall movement. During reproduction, the laser irradiates a second region to create a second temperature distribution that enhances signal detection without causing unwanted domain wall movement. This localized heating approach stabilizes domain walls while enabling high-density recording.
Solution Approach 2:
The patent employs preliminary action by pre-establishing different temperature distribution patterns before actual recording and reproduction operations. The system prepares distinct temperature fields in advance - a first temperature distribution for recording that promotes stable domain formation, and a second temperature distribution for reproduction that enhances signal detection. This preliminary temperature setup prevents unwanted domain wall movement during the actual operations.
3Device complexity
If same optical system is used for recording and reproduction, then device complexity is reduced, but signal detection quality deteriorates at high density
Solution Approach 1:
The patent applies local quality by using different optical parameters for recording and reproduction operations. While the physical optical system (lens, detector) remains the same, the system locally adjusts parameters such as laser wavelength, numerical aperture, and spot diameter to optimize for the specific operation being performed. This allows high-quality signal detection at high density without requiring completely separate optical systems.
Solution Approach 2:
The patent employs parameter changes by varying optical parameters including wavelength, numerical aperture, and spot diameter between recording and reproduction modes. These parameter adjustments enable the same physical optical system to achieve optimized performance for both recording and reproduction, thereby maintaining signal detection quality at high density without increasing device complexity.
4Quantity of substance
If high NA objective lens is used to increase recording density, then recording density is improved, but astigmatism from substrate tilt increases
Solution Approach 1:
The patent employs parameter changes by adjusting the numerical aperture and other optical parameters to optimize the balance between recording density and astigmatism. By carefully selecting and varying these parameters during recording and reproduction, the system achieves high-density recording while minimizing the harmful effects of astigmatism caused by substrate tilt.
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 enables the formation of stable high-density recording magnetic domains with improved signal characteristics and reduced interference, ensuring reliable information storage even at elevated temperatures and during repeated high-speed rewriting.
Implementation Method 1
the temperature of the magnetic recording medium is raised by the laser beam during recording
Implementation Method 2
the temperature of the magnetic recording medium is raised by a heating method for raising the temperature of a magnetic recording medium
Implementation Method 3
an external magnetic field is applied with a recording-use magnetic head so that information is recorded in the recording region
Implementation Method 4
information is reproduced by using a reproduction-use magnetic head (such as a GMR) to detect the magnetic flux from this residual magnetization
Implementation Method 5
GMR (giant magneto-resistive) heads that afford higher magnetic field sensitivity
Implementation Method 6
the temperature of the magnetic recording medium is raised by the laser beam, which increases the strength of residual magnetization in the recording region
Data Source
AI summary
A method for recording to and reproducing from a magnetic recording medium is disclosed in which an information signal is recorded and reproduced under thermal assist, and which allows one to stably record tiny recording magnetic domains and stably detect a reproduction output signal during reproduction when recording at high density. In this method, the temperature distribution in the information recording and reproduction region of the magnetic recording medium is controlled to be different during recording and during reproduction. This allows recording magnetic domains to be stabilized even when recording fine marks, and greatly increases the recording density because stable detection is possible without reducing the reproduction signal amplitude.