Temperature dependence of magnetization in Fe–Pd thin films

Abstract

Fe–Pd alloys containing about 30 at.% Pd are promising magnetic shape memory alloys and hence draw much attention by materials researchers due to their potential applications in magnetomechanical actuators and sensors. We have carried out magnetization measurements on the dc magnetron sputtered Fe 100− x Pd x thin films. In-plane magnetic hysteresis loops were obtained at 300 K, 77 K and 4.2 K for all the films. From the magnetization curves we have determined the saturation magnetization M s. At 300 K, the M s of the Fe 71Pd 29 film is about 950 emu/cm 3 which is considerably smaller than the other samples. Similar lower M s values were obtained for this film at 77 K and 4.2 K as well. Thus, at any given temperature, the M s of the Fe 71Pd 29 film is the lowest. This is an important observation because the itinerant ferromagnetic model predicts lower M s for this composition when compared with the other compositions. Structural transition is also reported at this composition. The M s reported in the literature for the Fe–Pd bulk alloys show a linear decrease with the Pd concentration. The coercivity observed in the Fe 71Pd 29 film is also the lowest when compared with other compositions, at any temperature. We presume that the coercivity observed in our films is due to grain size effect as the grain size generally plays a predominant role in thin films with nanometer size grains. The ZFC and FC measurements carried out on the films show normal ferromagnetic behaviour.