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 /spl sim/1.7 Oe, a high anisotropy field of /spl sim/37 Oe and 4/spl pi/M/sub s//spl sim/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 /spl sim/2.63 GHz, a relative permeability /spl mu/' of /spl sim/400-500 and a low dissipation /spl mu/" of 10-30 in the frequency range of 0.1-1 GHz. Upon subsequent annealing at 200-400/spl deg/C 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.