Grain growth and ordering kinetics in CoPt thin films

Grain growth and ordering kinetics have been studied in a 10-nm-thick CoPt alloy film of equiatomic composition annealed in the temperature range 550-700 degrees C by quantifying the grain size, grain size distribution, ordered fraction and ordered domain size. The mean grain size of the as-deposited films is 5 nm and the-film is fully face-centered cubic. Upon annealing in the temperature range 550-600 degrees C, the mean grain size reaches a stagnation limit of 27 nm and the grain size distribution is lognormal. Grain growth resumes beyond 600 degrees C and the mean grain size reaches as high as 55 nm at 700 degrees C. Ordering occurs by nucleation and growth of L1(0) ordered domains, with a mean size of 3 nm at 550 degrees C and 19 nm at 700 degrees C. The ordered fraction shows a dramatic increase from 1% to similar to 28% between the two extremes of annealing temperature. The increase in the coercivity of the annealed films follows the increase in the ordered fraction more closely than the increase in grain size. The shape of the M-H loop shows evidence of coupling between the magnetically hard (ordered) and soft (disordered) regions. (C) 1996 American Institute of Physics.