Magnetocrystalline anisotropy of partially ordered Fe-Pt nanoparticles directly synthesized by microwave-polyol method

Fe-Pt nanoparticles with L1₀ ordered structure are synthesized by microwave-polyol method at 250°C. The crystal structure and magnetocrystalline anisotropy of the nanoparticles are analyzed by X-ray diffraction and by rotational hysteresis loss measurement, respectively. The results are then evaluated at room temperature and compared with the nanoparticles prepared by conventional polyol method at 290°C. The anisotropy field, H_k, is much smaller for the conventional method (H_k = 1 kOe) than that for the microwave polyol method (H_k = 83 kOe with a coercivity of 3.4 kOe and saturation magnetization of 49 emu/g). However, the anisotropy-field distribution reveals that large amount of nanoparticles with lower anisotropy fields still exist in the sample prepared by the microwave-assisted polyol method.