FePt granular films with rare earth element oxides as ferromagnetic grain boundary materials

In this paper, systematic investigation results of nanostructure, magnetic properties and thermal properties of FePt-ferromagnetic grain boundary material granular films is reported. We used Fe3O4, Nd2O3, Sm2O3, Tb4O7, Eu2O3, CeO2, Gd2O3 as ferromagnetic grain boundary material (GBM). The separation of magnetic clusters is promoted and average magnetic cluster size (CS) of granular films with Sm2O3, Gd2O3 and CeO2 GBMs is less than 5 nm. There is a positive correlation between degree of order (Sin) and CS, such that Sin decreases when CS decreases. Here, Sin is derived from the integral intensity ratio of (110) and (220) diffractions from the in-plane XRD profiles. The saturation magnetization (Msfilm) of all FePt-ferromagnetic GBMs is higher than that of the FePt-C GBM. The reduction of blocking temperature standard deviation (σTb) is expected since the slope of the dependence of magnetization on temperature of the FePt-rare earth element oxide GBMs are larger than FePt-C GBM.