Tuning of soft magnetic properties in FeCoHfO thin films by various sputtering power and pressure

Abstract

FeCoHfO thin films with soft magnetic properties were deposited on Si (100) substrates using radio frequency reactive magnetron sputtering in Ar+O2 gases. During the deposition process, the partial pressure of oxygen was fixed at 3%. Sputtering power and sputtering pressure varied from 50 to 350 W and from 0·2 to 1 Pa respectively. In the condition of stationary sputtering gases pressure of 0·4 Pa, it was found that the film electrical resistivity ρ decreases steeply with the increasing sputtering power, and the natural ferromagnetic resonant frequency fr and static anisotropy field Hk increase with increase in power from 50 to 250 W, and then decrease when power exceeded 250 W. The coercivity of films had a contrary trend compared with fr. At 250 W sputtering powers, the optimal properties with fr≈3·02 GHz, saturation magnetisation 4πMs≈19·6 kGs, coercivity Hc≈2 Oe and ρ≈2200 μΩ cm were obtained. In the condition of fixed sputtering power of 250 W, fr, 4πMs and Hk decreased with the increases in sputtering pressure; Hc and ρ had an opposite trend. The physical nature of the effect was suggested to be related to the structure and composition changes in films.