Structural anisotropy in amorphous Fe-Tb thin films

We have used conventional and anomalous dispersion x-ray scattering to study the near-neighbor atomic environments in sputter-deposited amorphous Fe-Tb thin films with a large perpendicular magnetic anisotropy. The as-deposited films show a clear structural anisotropy, with more Fe-Tb near neighbor pairs in the out-of-plane direction. Upon annealing, the magnetic anisotropy drops significantly, and we see a corresponding reduction in the structural anisotropy. The number of Fe-Tb near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Fe-Tb near neighbors becomes more uniform upon annealing. We conclude that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure.