Development and optimisation of FeCoHfN soft magnetic thin films with high-frequency characteristics

Ferromagnetic amorphous Fe-Co-Hf-N thin films with a gradient concentration of Hf doping were fabricated by rf reactive magnetron sputtering. The evaluated magnetic properties and high-frequency characteristics were sensitive to the doping contents. In this study, a new technology was used to deposit a series of Fe-Co-Hf-N thin films on which gradient concentration of Hf was present. By this new deposited technology, the films existed residual stress, and thus the stress-induced anisotropy field was enhanced. Therefore, the as-deposited films without postannealing exhibited larger anisotropy field (H-k) of 150 Oe. In addition, coercivity (H-C) of less than 5 Oe in both easy and hard axes, and electrical resistivity (rho) of 500 mu Omega cm were obtained. The permeability measurement showed a permeability of around 100 at 3 GHz and a ferromagnetic resonance frequency (f(FMR)) in excess of 3 GHz. It is expected that this film should be promising for practical applications as a high-frequency ferromagnetic material. (C) 2008 Elsevier B. V. All rights reserved.