Ex situ annealing method for c-axis oriented barium ferrite thick films

A barium hexaferrite (BaFe12O19, magnetoplumbite structure, BaM) multilayered film, with a total thickness of 0.63 mum, was deposited on a Si substrate by stacking several 0.09 mum layers using a rf sputtering technique. Each 0.09 mum layer was ex situ annealed at 800degreesC for 10 min prior to deposition of the succeeding layer. A vibrating sample/torque magnetometer was employed to characterize the magnetic properties of both the BaM multilayered and a single layered film of the same thickness. The 0.63 mum thick BaM multilayered and single layered films show a squareness (SQ=M-r/M-s at 7 kOe) of 0.81 and 0.62, respectively. An anisotropy field (H-A) was found to be 17 kOe for the BaM multilayered film and 14.5 kOe for the single layered film. A stacking of BaM layers, with ex situ annealing between each layer, improves the c-axis orientation and anisotropy field as compared to a single layered film with the same thickness. This is attributed to limiting the number of nucleation sites for randomly oriented BaM crystallites existing in films thicker than 0.1 mum. (C) 2003 American Institute of Physics.