CoPtスパッタ膜の磁気特性

CoPt alloy films have been preapred by RF sputtering. Film thickness is 100nm and saturation magnetization Ms ranges from ~600 to ~1300 emu/cm3. In films prepared without substrate bias, the easy axis of magnetization lies in the film plane irrespective of Ms. However, perpendicular anisotropy is greatly enhanced by resputtering. In films prepared with the substrate bias of -80 V, the easy axis is perpendicular to the film plane, provided that Ms is within the range from ~800 to ~1000 emu/cm3. Perpendicular anisotropy in a resputtered film is greatly reduced by annealing in vacuum, while there is no significant difference between X-ray diffraction patterns before and after annealing. In films prepared without substrate bias, perpendicular coercivity is almost the same as in-plane coercivity, talking a maximum value of about 1.4 kOe when Ms≒950 emu/cm3. Perpendicular coercivity is hardly somewhat reduced by resputtering