High resistive Co–Fe–Hf–O magnetic thin films for high-frequency applications

Here, we present results of a systematic investigation of electrical and magnetic properties of Co–Fe–Hf–O thin films, which were deposited on Si(1 0 0) substrates by the oxygen reactive RF-sputtering method, at varying partial pressure of oxygen from 0 to 13%. Among the compositions investigated, we have achieved the optimal Co19.35Fe53.28Hf7.92O19.35 film with desired properties of high saturation magnetization, 4πMs ∼ 19.86 kG, low coercivity, Hc ∼ 1.5 Oe, high anisotropy field Hk ∼ 84 Oe, and high electrical resistivity ρ ∼ 3569 μΩ cm. This film also exhibits a stable constant frequency response of the magnetic permeability up to 3 GHz, and reaches a maximum at the ferromagnetic resonant frequency of 4.024 GHz. The excellent properties of this film make it ideal for uses in high-frequency applications of micromagnetic devices. The dependence of the electrical and magnetic properties of Co–Fe–Hf–O film on the oxygen concentration can be understood from the microstructural evolution of this material.