Exchange-coupling behavior in nanostructured FePt/Fe bilayer films

Different thicknesses of FePt/Fe bilayer films are deposited on (001) MgO substrates by sputtering Fe and Pt targets with in-situ heating at 830OC. X-ray diffraction indicates a complete alignment of the FePt [001] axis with MgO [001] axis. The nucleation field Hn is estimated from hysteresis loops measured using a SQUID magnetometer. A FePt/Fe bilayer model is proposed to calculate the nucleation field Hn and compared with the experimental data. The model can explain experimental trends and gives useful predictions for nanostructure synthesis and further experiment.