Barium ferrite films grown by laser ablation

Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al/sub 2/O/sub 3/ single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe/sub 12/O/sub 19/ 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 BaFe/sub 12/O/sub 19/ which becomes unstable. On the other hand, the presence of other phases such as Ba/sub 2/Fe/sub 6/O/sub 11/ and Fe/sub 2/O/sub 3/ is detected. The annealing study reveals the presence of a threshold temperature (629/spl deg/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.