The effects of the growth pressure and annealing conditions on perpendicular magnetic anisotropy of sputtered NdFeCo films on Si(1Â 1Â 1)

Series of NdFeCo thin films with strong perpendicular magnetic anisotropy (PMA) have been sputter-deposited onto Si substrate at elevated temperature of TS = 310 °C. The influence of sputtering pressure and annealing conditions on the micro/magnetic structure and PMA of the films have been investigated by XRD, FE-SEM, VSM, and MFM. With increasing growth pressure from PAr = 0.1 to 1.5 Pa, the compositional ratios of Fe/Nd and Co/Nd decrease monotonically, while the PMA shows a broad peak with maximum perpendicular anisotropy energy of Ku = 148 kJ/m3 at PAr = 0.9 Pa. The observed stripe domains exhibit a fascinating variety of configurations ranging from ordered parallel stripe to disordered labyrinthine patterns that depend on sputtering pressure induced residual stress or defects present in the films and magnetic history. The residual stress in the as-deposited films is evidenced by the subsequent rapid thermal annealing (RTA) experiments which show an obvious XRD peak shifting at annealing temperature of TA ⩽ 400 °C. It is interesting to find that there were Nd2Fe14Si3 and Nd6Fe13Si intermetallic compounds observed in the films processed by RTA at TA ⩾ 500 °C, while these silicides were not formed in the films annealed by conventional thermal annealing process. In contrast to the film on Si substrate, the NdFeCo film on glass substrate deposited at TS = 310 °C and PAr = 0.3 Pa showed a much weaker PMA with Ku = 38 kJ/m3. On the basis of the experimental results, it is suggested that the residual stress induced magnetoelastic anisotropy is the main origin of the PMA observed in high-temperature deposited NdFeCo film on Si substrate.