Comparison of magnetic and structural properties of permalloy Ni₈₀Fe₂₀ grown by dc and high power impulse magnetron sputtering

We study the microstructure and magnetic properties of Ni₈₀Fe₂₀ thin films grown by high power impulse magnetron sputtering (HiPIMS), and compare with films grown by dc magnetron sputtering (dcMS). The films were grown under a tilt angle of 35 to identical thickness of 37 nm using both techniques, at different pressure (0.13-0.73 Pa) and substrate temperature (room temperature and 100 C). All of our films display effective in-plane uniaxial anisotropy with square easy axis and linear hard axis magnetization traces. X-ray diffraction reveals that there is very little change in grain size within the pressure and temperature ranges explored. However, variations in film density, obtained by x-ray reflectivity measurements, with pressure have a significant effect on magnetic properties such as anisotropy field (H _k) and coercivity (H _c). Depositions where adatom energy is high produce dense films, while low adatom energy results in void-rich films with higher H _k and H _c. The latter applies to our dcMS deposited films at room temperature and high pressure. However, the HiPIMS deposition method gives higher adatom energy than the dcMS and results in dense films with low H _k and H _c. The surface roughness is found to increase with increased pressure, in all cases, however it showed negligible contribution to the increase in H _k and H _c.