Effects of La Doping on CaB$lt;inf$gt;6$lt;/inf$gt; Thin Films Prepared by DC Magnetron Sputtering

Both La doped and undoped Ca 1-x La x B 6 (x = 0, 0.01, 0.02, 0.03) thin films were prepared by direct current magnetron sputtering method. Morphology and thickness of these films were characterized by atomic force microscopy. Thicknesses of doped films were about twice that of the undoped films, while the grain growth of the film was much enhanced by La doping. X-ray photoelectron spectroscopy (XPS) was used for investigating the chemical composition of film surfaces. Calculated La/Ca atomic ratios were close to the theoretical values, and there were no other ferromagnetic impurities or elements especially iron existing in films. Ca 0.98 La 0.02 B 6 films exhibited the highest room temperature saturation magnetization 84.54 emu/cm 3 . The saturation magnetization decreased with increasing film thickness. B 6 vacancies may be the main source of magnetism. Other defects such as grain boundaries also affected the magnitude of magnetism.