Epitaxy barium ferrite thin films on LiTaO3 substrate

Barium hexaferrite (BaM) thin films were deposited on (0001) LiTaO3 substra tes by pulsed laser deposition. Effects of the substrate temperature and ox ygen gas pressure on the formation and quality of these films were studied. Films deposited at a substrate temperature of 800 degrees C and an oxygen pressure around 0.23 mbar showed the best c axis normal to the film plane w ith locked in-plane orientation. The saturation magnetization M-s and aniso tropy field H-a measured by vibrating sample magnetometer were almost the s ame as those reported on bulk barium ferrite. Decreasing oxygen pressure hi nders the formation of the Ba layer in BaM magnetoplumbite structure and gi ves rise to the spinel phase, which greatly decreases coercivity H-c of the films and finally destroys the whole BaM structure. Effects of the lattice mismatch and substrate-induced strains on the film structure were also stu died. It was found that barium ferrite thin films grown on LiTaO3 substrate s tend to choose a matching mode with compressional strains rather than she ar strains. (C) 1999 American Institute of Physics. [S0021-8979(99)05515-2] .