Magnetic properties of CoFeP films prepared by electroless deposition

Structure and magnetization of CoFeP films prepared by the electroless deposition were systematically investigated by varying the bath composition and deposition parameters to optimize soft magnetic properties. The cobalt content in the CoFeP films varies from 40.4 to 94.9 wt% by controlling the bath composition. Increase of the metallic ratio FeSO4·7H2O/(CoSO4·7H2O+FeSO4·7H2O) affects the films’ microstructure, which switches from amorphous to crystalline structure. The magnetic properties of CoFeP films reveal that the coercivity (Hc) values range from 80 up to 185 A/m and the saturation magnetization (Ms) from 82 to 580 eum/g depending on the bath composition, deposition parameters and heat-treatment conditions. Increase of Ms and remanent magnetization (Mr) as well as decrease of Hc are observed for the CoFeP films with bath pH, temperature and the metallic molar ratio increasing. It is also found that the Hc is enhanced with the increase of NaH2PO2·H2O concentration. CoFeP films showing good soft magnetic properties with coercivities less than 140 A/m and Ms close to 600 emu/g can be obtained in high pH bath and thereafter heat treatment. The deposit is found to be suitable as soft magnetic materials for core materials.