Juro Endo1, Tomoyuki Ohnuma2, Yoshihiko Hirotsu3 and Yukio Ichinose3
1Graduate Student, Nagaoka University of Technology, Nagaoka
Co80Ni20 alloy films with suitable magnetic properties for the high density magnetic recording were prepared by sputtering in the atmosphere of Ar-N2 gas mixture and by subsequent annealing at 593 K in vacuum. Microstructural morphologies and magnetic domain configurations of these films before and after annealing were observed by transmission electron microscopy, and the relation between the microstructures and magnetic properties was studied. As-sputtered films are non-magnetic and have amorphous structures due to the inclusion of nitrogen atoms. After the annealing, however, most of the nitrogen diffused out from the films and showed hard magnetic properties. A high coercivity of about 80 kA/m was obtained for the film prepared under a certain nitrogen content in sputtering. The electron microscopic observation of the high coercivity films showed that the ferromagnetic Co80Ni20 crystanllites with a (001) in-plane orientation are isolated individually by pore-like amorphous non-magnetic regions containing 30--50 mol% nitrogen. By the Lorentz electron microscopic observation, it was shown that the magnetic domain is finely configurated in the case of the high coercivity films. The high coercivity obtained in this study was explained well by the single domain particle theory.
Co80Ni_20 alloy film, magnetic recording media, sputtering, microstructure morphology, magnetic domain, transmission electron microscopy, magnetic property
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