Structure and magnetic properties of barium hexaferrite films deposited at low oxygen pressures

Barium hexaferrite films were grown by pulsed laser ablation deposition onto c-plane sapphire at oxygen pressures from 1 to 200mTorr to evaluate their structural and magnetic properties. Films deposited at pressures above 1mTorr showed excellent c-axis orientation normal to the film plane, and good surface morphologies. The c-axis lattice constant of films deposited at and above 50mTorr was reduced compared to bulk values. Film saturation magnetization values were slightly lower than bulk values, while anisotropy field values were comparable. Ferrimagnetic resonance measurements showed distinct absorption peaks, with the narrowest linewidth of 0.20kOe being measured for a 10mTorr film. The 1mTorr film had a significantly different texture wherein the c-axis laid down into the film plane, and also showed in-plane six-fold magnetic anisotropy. These results may indicate that highly c-axis oriented barium hexaferrite films can be grown to greater thicknesses using reduced oxygen pressures.