Magnetic behaviour of as-deposited and rapid thermal annealed Pr-Fe thin films

In the present work structure, microstructure and magnetic behaviour of e-beam evaporated Pr-Fe thin films was investigated in as-deposited and rapid thermal annealed conditions. The films were deposited on Si 〈100〉 substrates at room temperature. Structural studies carried out employing X-ray diffraction indicated that the as-deposited films were completely amorphous in nature. Upon rapid thermal annealing, presence of Fe phase could be observed from the X-ray diffraction patterns. Field emission gun scanning electron microscopy studies confirmed the presence of Fe nano-crystalline grains surrounded by amorphous Pr-Fe matrix with the number of nucleation sites increasing with increasing annealing temperature. Magnetization studies showed weak ferromagnetic behaviour for the as-deposited films whereas rapid thermal annealed films exhibited strong in-plane magnetic anisotropy owing to the presence of Fe nano-crystalline grains. Saturation magnetization estimated from the in-plane magnetization curves was found to increase with increasing annealing temperature up to 450 °C although with further increase in annealing temperature to 550 °C it decreased. A minimum coercivity of about 1.6 kA/m was observed for the Pr-Fe film annealed at 450 °C. Magnetostriction measurements indicated increase in magnetostriction with increasing annealing temperature up to 450 °C. A maximum magnetostriction of about 100 μ-strains was achieved for the film annealed at 450 °C.