Book contents
- Frontmatter
- Contents
- Preface
- 1 Overview of Optical Data Storage
- 2 Optics of Gaussian Beams
- 3 Theory of Diffraction
- 4 Diffraction of Gaussian Beams from Sharp Edges
- 5 Optics of Thin Films and Multilayers
- 6 Magneto-optical Readout
- 7 Effects of High-numerical-aperture Focusing on the State of Polarization
- 8 Computer Modeling of the Optical Path
- 9 Noise in Magneto-optical Readout
- 10 Modulation Coding and Error Correction
- 11 Thermal Aspects of Magneto-optical Recording
- 12 Fundamentals of Magnetism and Magnetic Materials
- 13 Magnetostatics of Thin-film Magneto-optical Media
- 14 Mean-field Analysis of Amorphous Rare Earth–Transition Metal Alloys
- 15 Magnetization Dynamics
- 16 Origins of Coercivity
- 17 The Process of Thermomagnetic Recording
- 18 Media Characterization
- References
- Index
15 - Magnetization Dynamics
Published online by Cambridge University Press: 07 September 2010
- Frontmatter
- Contents
- Preface
- 1 Overview of Optical Data Storage
- 2 Optics of Gaussian Beams
- 3 Theory of Diffraction
- 4 Diffraction of Gaussian Beams from Sharp Edges
- 5 Optics of Thin Films and Multilayers
- 6 Magneto-optical Readout
- 7 Effects of High-numerical-aperture Focusing on the State of Polarization
- 8 Computer Modeling of the Optical Path
- 9 Noise in Magneto-optical Readout
- 10 Modulation Coding and Error Correction
- 11 Thermal Aspects of Magneto-optical Recording
- 12 Fundamentals of Magnetism and Magnetic Materials
- 13 Magnetostatics of Thin-film Magneto-optical Media
- 14 Mean-field Analysis of Amorphous Rare Earth–Transition Metal Alloys
- 15 Magnetization Dynamics
- 16 Origins of Coercivity
- 17 The Process of Thermomagnetic Recording
- 18 Media Characterization
- References
- Index
Summary
Introduction
Thermomagnetic recording involves the laser-assisted nucleation and growth of reverse-magnetized domains under the influence of external and/or internal magnetic fields. The nature of nucleation, the speed and uniformity of growth, and the local pinning of domain boundaries due to structural inhomogeneities of the material are among the factors that determine the final shape and size of recorded domains. Since it is important to control domain size, while avoiding nonuniformities and jagged boundaries, and since it is important to create stable domains, a knowledge of magnetization-reversal dynamics, including the effects of the nanostructure within the “amorphous” material, is desirable.
The observed magnetization reversal in RE–TM films is a nucleation and growth process. During bulk reversal (at temperatures not too close to the Curie point Tc) the nucleation sites are mostly reproducible. Rather than being driven by thermal fluctuations, nucleation is believed to be rooted in the nonuniform spatial distribution of the structural and magnetic properties of the media. The measured hysteresis loops generally have high squareness, which indicates that the coercivity of wall motion is less than the nucleation coercivity. In other words, once the nuclei are created at a certain applied field, they continue to grow without further hindrance. The recording and erasure processes rely on the creation and annihilation of reverse-magnetized domains. High densities are achieved when the recorded domains are small and uniform, have smooth boundaries, and are precisely positioned.
- Type
- Chapter
- Information
- The Physical Principles of Magneto-optical Recording , pp. 543 - 585Publisher: Cambridge University PressPrint publication year: 1995
- 2
- Cited by