Coercivity in amorphous Tb-Fe alloys

The perpendicular magnetic anisotropy, coercive field, and initial magnetiz ation curves of amorphous TbxFe1-x (x between 0.15 and 0.32) were measured at room temperature for samples prepared under a wide variety of preparatio n conditions, including both e-beam co-evaporation and dc magnetron cosputt ering. The effect of growth temperature, annealing, and thickness were inve stigated. The perpendicular magnetic anisotropy shows little dependence on substrate type, sample thickness, or details of the deposition such as sput tering or e-beam evaporation, but is strongly dependent on growth temperatu re, increasing with increasing growth temperature up to nearly 300 degrees C. Coercivity on the other hand is extremely dependent on microstructure, a nd hence, on details of preparation, substrate type, and thickness. It is m uch larger in evaporated films than in similarly prepared dc magnetron sput tered films. Normalized coercivity decreases monotonically with increasing growth temperature. The dominant mechanism appears to be domain wall pinnin g in the bulk of the film due to columnar microstructure. High growth tempe rature stabilizes the material against subsequent annealing which tends to eliminate the anisotropy and, more slowly, the coercivity. (C) 1999 America n Institute of Physics. [S0021-8979(99)08314-0].