Evaluation of Atomic Layer Stacking Structure and Curie Temperature of Magnetic Films for Thermally Assisted Recording Media (Invited)

Thermally assisted recording system is a promising candidate to overcome the trilemma of perpendicular magnetic recording hard disk drive development. In this paper, we introduce our current research about evaluation for the media material. In-plane X-ray diffraction technique is effective to evaluate atomic layer stacking structure of (111)-oriented face-centered cubic, c-plane-oriented hexagonal closed packed (hcp), and their intermediate structure with stacking faults of CoPt alloy thin film. Analytical results of Co50Pt50-based thin film shows that changing the valence electron number closer to 9 can effectively reduce the stacking fault. In practical, perfect hcp atomic layer stacking can be achieved by substituting Pt (group 10) with Rh (group 9). High-angle annular dark field of scanning transmission electron microscopy with probe diameter of 1 Å can effectively observe composition modulated atomic layer stacking with the super-lattice diffraction in Co-based alloy films. In practical, for Co80M20 (M: Ir, Pt) thin film sputtered under high substrate temperature, the irregular or alternately layered structure of M rich and M poor layer can be observed directly. To evaluate Curie temperature (TC), which is an important physical property of thermally assisted media, conduction electron spin-dependent scattering should be the focus. Fitting dielectric spectra for MnSb thin film with TC ~ 320^°C measured with the ellipsometry and analyzing the Drude´s term, temperature dependence of resistivity and scattering time at around TC was confirmed.