Soft magnetic and high-frequency properties of Ni-Zn ferrite film with FeMn underlayer

Ni_0.45Zn_0.55Fe₂O₄ (40 nm) single-layer and Fe₅₀Mn₅₀ (25 nm)/Ni_0.45Zn_0.55Fe₂O₄ (40 nm) bilayer films were prepared on Si(111) substrates by radio frequency magnetron sputtering at room temperature, and the influence of FeMn underlayer on the microstructure and magnetic property of Ni-Zn ferrite film has been investigated. It was found that the introduction of Fe₅₀Mn₅₀ underlayer resulted in a decrease from 7.1 to 3.1 kA/m in coercivity and increase from 0.22 to 0.60 in residual magnetization ratio of the ferrite film. The complex permeability μ = μ′ − iμ″ values of the films were measured at a frequency of up to 5 GHz. An obvious resonance peak at about 1.65 GHz of the bilayer film appeared in the permeability spectrum. The reason has been researched preliminarily and was ascribed to the change of the film's microstructure with FeMn underlayer.