High-frequency ferromagnetic properties of multilayered FeCoHfO/AlOx films

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 ∼ 100 at 100 MHz and ferromagnetic resonance frequency over 3 GHz) and high resistivity (ρ ∼ 1088) μΩ cm were achieved.