Soft magnetism and microwave magnetic properties of Fe-Co-Hf films deposited by composition gradient sputtering

A composition gradient sputtering method was employed to deposit a series of (Fe x Co 1-x ) 1-y Hf y alloy films with different Fe/Co atomic ratios and Hf-doping. At Fe/Co=70/30, the magnetically annealed (Fe 0.7 Co 0.3 ) 1-y Hf y films with y=0.087 - 0.124 showed a very high uniaxial anisotropy and an ultrahigh ferromagnetic resonance frequency over 7 GHz after the films were annealed at 350°C, while at Fe/Co=50/50, the as-deposited (Fe 0.5 Co 0.5 ) 1-y Hf y films with y=0.074 - 0.168 showed an excellent in-plane uniaxial anisotropy and high ferromagnetic resonance frequency over 3 GHz. These Fe-Co-Hf films deposited by the composition gradient sputtering method exhibited ahigh saturation magnetization of 1.8-2.2 T, a large uniaxial anisotropy field of 200-500 Oe, and a high ferromagnetic resonance frequency over 7 GHz, which provides great opportunities for integrated magnetic devices.