Magnetic properties of amorphous Sm-Fe and Sm-Fe-B thin films fabricated by radio-frequency magnetron sputtering

Magnetic properties of giant magnetostrictive Sm-Fe and Sm-Fe-B thin films are systematically investigated over a wide composition range from 14.1 to 71.7 at. % Sm. The amount of B added ranges from 0.3 to 0.8 at. %. The microstructure mainly consists of an amorphous phase in the intermediate Sm content range from 20 to 45 at. %. Together with an amorphous phase, crystalline phases of Fe and Sm also exist at low and high ends of the Sm content, respectively. Well-developed in-plane anisotropy is formed over the whole composition range, except for the low Sm content below 15 at. % and the high Sm content above 55 at. %. As the Sm content increases, the saturation magnetization decreases linearly and the coercive force tends to increase, with the exception of the low Sm content where very large magnitudes of the saturation magnetization and the coercive force are observed due to the existence of the crystalline alpha-Fe phase. The coercive force is affected rather substantially by the B addition, resulting in lower values of the coercive force in the practically important Sm content range of 30-40 at. %. (C) 1998 American Institute of Physics. [S0021-8979(98)25511-3].