Effect of process temperature on structure, microstructure, residual stresses and soft magnetic properties of sputtered Fe70Co30 thin films

• The properties of Fe70Co30 thin films with substrate and post-annealing temperatures are studied.
• Good combination of Ms and Hc were observed in the films with different substrate temperatures.
• Coercivity decrease is attributed to the increased grain size and smaller residual stresses.

The effect of substrate and post-annealing temperatures on the structure, microstructure, residual stresses and soft magnetic properties of Fe70Co30 thin films was systematically investigated. Microstructural studies reveal that the films are continuous and undergo changes in shape of grain from plate like to spherical resulting in an increase in grain size with the increase in substrate temperature, whereas the post-annealed films show small pores and no significant grain growth till 500 °C. Coercivity (Hc) was found decreasing with both the substrate and post-annealing temperatures; however, the best Hc value of 26 Oe was obtained for the films deposited at substrate temperature of 500 °C. The post-annealed films exhibited relatively higher Hc values. A good combination of high saturation magnetization 4πMs of ~23.2 kG and low coercivity Hc of 26–65 Oe was obtained for the films deposited at substrate temperature of 450–500 °C. Residual stress analysis on films with different substrate temperatures shows the presence of tensile stress. The decrease in tensile stress is attributed to the relaxation of thermal stresses in the films.