Ferromagnetic properties of fcc Gd thin films

摘要

Magnetic properties of sputtered Gd thin films grown on Si (100) substrates kept at two different temperatures were investigated using X-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements. The obtained Gd thin films have a mixture of hcp and fcc structures, but with their fractions depending on the substrate temperature T_s and film thickness x. Gd fcc samples were obtained when T_s = 763 K and x = 10 nm, while the hcp structure was stabilized for lower T_s (300 K) and thicker film (20 nm). The fcc structure is formed on the Ta buffer layer, while the hcp phase grows on the fee Gd layer as a consequence of the lattice relaxation process. Spin reorienta-tion phenomenon, commonly found in bulk Gd species, was also observed in the hcp Gd thin film. This phenomenon is assumed to cause the magnetization anomalous increase observed below 50 K in stressed Gd films. Magnetic properties of fcc Gd thin films are: Curie temperature above 300 K, saturation magnetization value of about 175 emu/cm~3, and coercive field of about 100 Oe at 300 K; features that allow us to classify Gd thin films, with fee structure, as a soft ferromagnetic material.