Thickness dependence of the magnetic properties of high-coercive Pr–Fe–B thin films with perpendicular magnetic anisotropy

The magnetic properties of Pr–Fe–B films with perpendicular magnetic anisotropy have been studied as a function of thickness varying from 10 to 1200 nm. The crucial thickness for forming the Pr2Fe14B phase is estimated to be about 25 nm in our study, and the perpendicular anisotropy shows a trend to vanish for thick films. The coercivity of the films initially increases with increasing film thickness, gradually reaching a value which is near the value for bulk material. The magnetic domain size increases with increasing thickness. The surface morphology, the roughness and the domain structure of the films have been investigated by means of atomic-force microscopy and magnetic-force microscopy.