Structure and magnetic properties of high coercive NdFeB films with a perpendicular anisotropy

Relatively good hard magnetic properties obtained from Nd2Fe14B films prepared by the rf sputtering technique were investigated in terms of the microstructural development. Although as-deposited films on Mo substrates deposited at substrate temperatures (Ts) of 365 °C were amorphous with the dispersion of nanocrystalline NdO particles, columnar grains of Nd2Fe14B phase with the c-axis perpendicular to the film plane developed after annealing at 650 °C at an optimized heating rate. Nd2Fe14B grain size was about 400 nm in average and NdO particles of about 10 nm were dispersed within the grains and along the grain boundaries. These films exhibited good perpendicular hard magnetic properties of iHc=1356 kA/m and (BH)MAX∼216 kJ/m3.