Variation in material parameters for hexagonal barium ferrite films on (111) magnesium oxide as a function of oxygen pressure

This work examines the material characteristics and magnetic properties of hexagonal M-type barium ferrite (BaFe12O19) films deposited by pulsed laser ablation deposition onto (111) magnesium oxide substrates at different oxygen growth pressures. X-ray diffraction data showed the lattice constant of the film grown at 300 mTorr c=23.23 Angstrom increased to c=23.30 Angstrom for the film grown at 20 mTorr. The saturation magnetization ranged from 4.03 to 4.33 kG and the magnetic uniaxial anisotropy field ranged from 16.73 to 19.49 kOe as the oxygen pressure was varied from 10 to 300 mTorr. The narrowest ferrimagnetic resonance (FMR) linewidths (DeltaH) for as-produced films were obtained for the 10 mTorr films, where DeltaH=0.39 kOe. Films grown with oxygen pressure at 200 mTorr or higher showed two distinct resonance modes, which exhibited DeltaH(1)greater than or equal to0.90 kOe and DeltaH(2)greater than or equal to1.10 kOe at 59 GHz for a film deposited at 925 degreesC. The FMR linewidths for this film decreased to DeltaH(1)=0.52 kOe and DeltaH(2)=0.45 kOe after annealing the film at 1000 degreesC for 1 h. These results indicate that thick films grown at higher oxygen pressures have magnetic parameters closer to bulk values, but also show larger magnetic losses than films grown at lower oxygen pressures. (C) 2002 American Institute of Physics.