Effect of post-annealing on ultra-high frequency properties of amorphous Fe-Co-B thin films

In this paper, FeCoB amorphous thin films were deposited on glass substrates using a triode sputtering source under a uniform applied magnetic field. The as-deposited films exhibit a low coercivity of similar to1.7 Oe, a high anisotropy field of similar to 37 Oe and 4 piM(s) similar to 17.5 kG, when sputtered with a bias voltage of 180 V. The large anisotropy fields and saturations in these films result in a ferromagnetic resonance frequency as high as similar to2.63 GHz, a relative permeability mu' of similar to 400-500 and a low dissipation mu" of 10-30 in the frequency range of 0.1-1 GHz. Upon subsequent annealing at 200-400 degreesC for 2 hrs, the magnetic properties of the films are found to be affected significantly. The magnetic properties of the as-deposited and the annealed films have been compared with a considering of the microstructure modification during annealing.