Effects of Nickel addition on the microwave permeability spectra of sputtered Fe–Co–Ni–B thin films

In order to develop the materials with high-frequency characteristics, the effects of Ni addition on the microwave permeability spectra of sputtered FeCoNiB thin films have been investigated in the range of 0.5–5 GHz by a shorted microstrip transmission line perturbation method. It is found that films with appropriate low Ni content exhibit excellent high-frequency characteristics resulting from the B segregation on grain boundaries: the real part of permeability at 0.5 GHz, the ferromagnetic resonance frequency, and the resistivity achieve 332, 3.16 GHz and 276 μΩ cm, respectively. Meanwhile, the degeneration of the soft magnetic properties and high-frequency characteristics occurs in the films with high Ni content, owing to the increase of metallic phase and anisotropy dispersion. As a result, appropriate increment of Ni content is of advantage to soft magnetic properties and high-frequency characteristics.