Barium ferrite films grown by laser ablation

Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al₂O₃ single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe₁₂O₁₉ phase, very well oriented with (001) texture, and exhibit a large perpendicular magnetic anisotropy. In this case, the microstructure and the anisotropy orientation are not influenced by variation of the oxygen pressure in the range 20-530 mtorr, but the coercivity and the remanence are affected. Films prepared without oxygen are isotropic. XRD measurements reveal the absence of the BaFe₁₂O₁₉ which becomes unstable. On the other hand, the presence of other phases such as Ba₂Fe₆O₁₁ and Fe₂O₃ is detected. The annealing study reveals the presence of a threshold temperature (629°C) for the appearance of the magnetisation and the anisotropy orientation. This temperature also corresponds to the onset in growth of the crystalline structure of barium ferrite. In the latter case, the coercivity was found to be greatly reduced by the increase in grain size at higher annealing temperatures