High-frequency responses of granular CoFeHfO and amorphous CoZrTa magnetic materials

High-resistivity soft magnetic materials are receiving much attention as they have relatively low core loss at high frequencies. We developed magnetically soft granular CoFeHfO material by pulsed-dc reactive magnetron sputtering and compared its electrical and magnetic properties, especially permeability spectra, with those of amorphous CoZrTa material. We also investigated the permeability spectra of patterned CoFeHfO films with different thicknesses and observed their magnetic domain structures by Kerr imaging microscopy. The granular CoFeHfO material has a better high-frequency response than the amorphous CoZrTa at thicknesses beyond similar to 0.5 mu m, if the ratio of the real/imaginary parts of the permeability is the principal figure of merit, and is an excellent candidate for high-frequency applications such as integrated magnetic inductors.(c) 2007 American Institute of Physics.