CHANGES IN FILM STRUCTURE AND INCREASE IN COERCIVITY FOR CO/PD MULTILAYERED FILMS WITH ATMOSPHERIC ANNEALING

Co/Pd multilayered films exhibit large perpendicular magnetic anisotropy and have attracted attention as new materials for recording media and for other applications. The coercivity (H(c)), however, is small in as-sputtered films, We have found that H(c) increased markedly with the atmospheric annealing at 300-degrees-C to 2 kOe, and studied the change in film structure and reason of the increase in H(c) with the annealing. The rf magnetron sputtering method was employed in fabricating the films. Film structure changes were observed by x-ray diffraction, Auger electron spectroscopy, transmission electron microscopy, energy dispersive x-ray spectrography, and atomic force microscopy, The increase in H(c) was observed only in the atmospheric annealing, and not in the vacuum-annealing. The internal structure of films after the atmospheric annealing at 300-degrees-C consisted of columnar parts that had the multilayered structure that undertook vertical magnetization and column boundaries being surrounded by Co oxides. As a consequence, domain wall binding occurs in the segregated areas of the oxides in the column boundaries, thereby increasing H(c).