Magnetic Anisotropy and Coercivity in Magneto-Optical Recording Materials (original) (raw)
1999, Journal of the Magnetics Society of Japan
The perpendicular magnetic anisotropy of both amorphous Tb-Fe and crystalline fcc Pt-rich Co-Pt alloys is enhanced by increasing growth temperature, up to the onset of significant bulk atomic mobility (approximately one third of the melting temperature). High growth temperature also stabilizes these materials against subsequent annealing which tends to eliminate the anisotropy. The dependence on growth temperature can be fit with a two-level systems analysis in which the low energy surface state during growth is anisotropic. The source of this low energy state is suggested to be related to surface segregation for the Co-Pt alloys. The anisotropy for both materials shows very little dependence on substrate type, sample thickness, or details of the deposition such as sputtering or e-beam evaporation. Coercivity on the other hand is extremely dependent on microstructure and hence on details of preparation, substrate type, thickness, and crystallographic orientation. For a-Tb-Fe, the dominant mechanism appears to be domain wall pinning by microstructural defects in the bulk of the film, such as columnar microstructure.
Related papers
Preparation of Fe/Pt Films With Perpendicular Magnetic Anisotropy
IWNMS 2004, 2005
Magnetic layers with a high perpendicular magnetic anisotropy appears as an attractive solution to increase the information density in magneto optic recording media. Currently longitudinal magnetic recording systems reach densities of 10 Gbits/in.2, while computer simulations based on ...
Journal of Applied Physics, 1988
Perpendicular magnetic anisotropy (PMA) and dynamic magnetization reversal process in [CoFeB t nm/Pd 1.0 nm] n (t = 0.4, 0.6, 0.8, 1.0, and 1.2 nm; n = 2 -20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an effective uniaxial anisotropy up to 7.7×10 6 Jm −3 and a saturation magnetization as low as 200 emu/cc are achieved. Surface/interfacial anisotropy of CoFeB/Pd interfaces, the main contribution to the PMA, is separated from the effective uniaxial anisotropy of the films, and appears to increase with the number of the CoFeB/Pd bilayers. Observation of the magnetic domains during a magnetization reversal process using polar magneto-optical Kerr microscopy shows the detailed behavior of nucleation and displacement of the domain walls.
MAGNETIC ANISOTROPY GRADED MEDIA AND Fe-Pt ALLOY THIN FILMS
Anisotropy graded media are promising to overcome the writability problem in achieving ultrahigh areal density for magnetic recording media. To more conveniently study and compare various media with regard to a particular figure of merit, a new energy landscape method of analysis is suggested. Using this method, the theoretical limit of the figure of merit for a graded medium is found to be 4. This limit can be approached by a graded medium with I am indebted to my dissertation committee,
Observations of Domain Nucleation and Growth in Magneto-Optical Recording Media
Observations of micromagnetic dynamics in magneto-optical recording media have been performed using a static tester and a loop tracer. The magnetization reversal, domain structure and annealing treatment of amorphous rare earth-transition metal (RE-TM) alloy fIlms as well as multilayered cobalt-platinum (Co/Pt) thin films have been studied. The magnetization reversal was investigated in both nucleation-dominated and wall-motion-dominated media. The degree of jaggedness of various domain structures has been compared in terms of the fractal dimension of domains. We find that the magnetization reversal processes are intimately related to the jaggedness of domain surface. The fractal dimension increases monotonically from wall-motion-dominated films to nucleation-dominated films. The relationships between the hysteresis loop and the reversal process are also discussed.
Magnetocrystalline and Magnetic Surface Anisotropy in Nonepitaxial [Fe/Pt]$_{n}$ Multilayer Films
IEEE Transactions on Magnetics, 2000
The FePt thin films with [Fe/Pt] multilayer structure have been prepared on preheated Corning 1737F glass substrate using pure Fe and Pt target in a CMS-18 sputtering system. The dependence of FePt's perpendicular anisotropy on the multilayer structure was investigated. It was found that the perpendicular coercivity and remanence ratio could be enhanced in the FePt films by an optimization of the multilayer structure. The mechanism of the perpendicular anisotropy in [Fe/Pt] multilayer films was analyzed using the micromagnetic models, with careful discussions of the crystalline and interface anisotropies. It was found that the Fe/Pt interfaces play an important role in favoring the perpendicular orientation in the [Fe/Pt] multilayer films.
Growth-induced magnetic anisotropy and clustering in vapor-deposited Co-Pt alloy films
Physical Review B, 1999
͑111͒-oriented CoPt 3 and Co 0.35 Pt 0.65 films were deposited at various growth rates and over a range of growth temperatures from Ϫ50 to 800°C. Films grown at moderate temperatures ͑200-400°C͒ exhibit remarkable growth-induced properties: perpendicular magnetic anisotropy and large coercivity, as well as enhanced Curie temperature and low-temperature saturation magnetization. Magnetic measurements indicate significant Co clustering in these epitaxial fcc films. These properties are independent of crystallographic orientation, increase with increasing growth temperature, and vanish with annealing. We propose that the correlation between magnetic inhomogeneity, magnetic anisotropy, and enhanced moment is explained by clustering of Co into thin platelets in a Pt-rich lattice. This clustering occurs at the growth surface and is trapped into the growing film by low bulk atomic mobility. ͓S0163-1829͑99͒09041-4͔
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.