For mobile communication, the ferromagnetic resonance frequency of magnetic films must be over 3 GHz. A suitable anisotropic field and high resistivity for high frequency applications were obtained by inserting insulator (AlOx) layers into ferromagnetic layers (FeCoHfO). With this optimum configuration of three layers structure [FeCoHfO (400 nm)/AlOx (10 nm)](3), high frequency characteristics (permeability similar to 100 at 100 MHz and ferromagnetic resonance frequency over 3 GHz) and high resistivity (rho similar to 1088) mu Omega cm were achieved. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.