Nanogranular nickel iron thin films for high frequency power applications

Multi-layer nickel-iron-zirconia granular thin films were prepared using magnetron sputtering of NiFe and Zr targets in an Ar+O₂ mixture. The resulting films showed strong uniaxial in-plane anisotropy and good soft magnetic properties which are promising for high frequency power applications. The material exhibited low hysteresis loss when excited along the hard-axis direction and is expected to have low eddy current losses at high frequencies due to the high in-plane resistivity and insulation layers between the granular magnetic layers. The core loss of the thin film is predicted to be significantly lower than commercial nickel-zinc and manganese-zinc ferrites, when excited with a peak ac flux density between 0 and 200 mT. A high relative permeability of 540 makes the material useful for applications such as transformers and coupled inductors.