Magnetostriction and thin-film stress in high magnetization magnetically soft FeTaN thin films

Abstract

Domain structures in thin-film heads can be significantly influenced by magnetoelastic anisotropy. In this study we have undertaken systematic measurements of magnetostriction and stress in as-deposited and annealed states in FeN and FeTaN single-layer thin films with varying nitrogen contents. Magnetostriction was positive for FeN films, increased with increasing nitrogen content, and shifted toward negative values after annealing. Stress in as-deposited FeN films was tensile and decreased (became more compressive) with increasing nitrogen content. Annealing the FeN films resulted in significant stress relief. By contrast, magnetostriction was found to be negative for simple FeTa (zero nitrogen) and increased linearly with increasing nitrogen content to positive values. The magnetostriction in FeTaN did not change significantly after annealing at 200 and 250 °C. FeTaN film stresses were compressive in the as-deposited state and increased in magnitude (became more compressive) with increasing nitrogen content. After annealing these stresses were relieved slightly. Ta has been found to be very effective in enhancing the thermal stability of the FeN films.