Effect of nitridation on magnetic properties of Fe53Pt47 thin film

The Fe53Pt47 thin films with varying thickness were prepared using dc magnetron sputtering at various substrate temperatures (i.e., from 250 to 600 degreesC) on to CrMo seeded glass substrates. The powder x-ray diffraction studies reveal that the ordered fct gamma(2)-FePt phase begins to appear starting from the substrate temperature of 250 degreesC. The estimated ordering parameters show that the films prepared at 300 degreesC are well ordered and ordering parameters increase slowly as increasing substrate temperatures. On nitridation of the Fe53Pt47 thin films, expansion of the face centered tetragonal crystal lattice along the c axis is observed. The saturation magnetization is decreased with decreasing film thickness. This has been explained mainly on the basis of size and surface effects of nanocrystals in the films including intergranular interactions. Maximum coercivity of 8.7 kOe is observed for the film thickness of 350 nm. The drastic decrease in magnetization with the increase in nitridation time duration has been attributed to the spin pairing effects as a result of electron supply from interstitial nitrogen atoms to the 3d bands of iron atoms. We observed an increase of H-c from 7.8 kOe for non-nitrided Fe53Pt47 film to 10.8 kOe for a 3 h nitrided film. (C) 2002 American Institute of Physics.