Microstructural and magnetic study of nanocrystalline soft magnetic thin films of Fe-C and Fe-Co-C deposited with sputtering

Fe-C and Fe-Co-C thin films are deposited at various conditions by sputtering. Microstructural analyses reveal that these films consist of nanocrystals with higher magnetic moment and lower carbon contents which are dispersed in amorphous matrix with lower moment and higher carbon contents. The sputtering conditions strongly influence internal stress in the films. Magnetic properties are strongly influenced by the internal stress compared with the microstructure due to the magnetostriction effect. It is necessary to fabricate stress-free films to obtain appropriate soft magnetic properties such as low coercivity and appropriate uniaxial anisotropy. In the case of Fe-Co-C films, the lowest coercivity of 12 Oe in hard axis is obtained with the saturation flux density of 2.4 T. The Fe-Co-C films exhibit better frequency characteristics than Fe-C films due to higher anisotropy field and saturation flux density.