High frequency soft magnetic properties of nanocrystalline Fe-(Co)-Hf-O films with high electrical resistivity and their application to micro DC-DC converter

We have developed nanocrystalline Fe-(Co)-Hf-O films which exhibit high electrical resistivity (ϱ) more than 4 μ Ωm as well as high magnetization (Is) more than 1T and also good soft magnetic properties even in as-deposited states. Furthermore, real part of complex permeability μ′ of these films exhibit more than 1000 up to 100 MHz by annealing in an uniaxial magnetic field.