Giant negative magnetoresistance in perovskitelike La_2/3Ba_1/3MnO_x ferromagnetic films

At room temperature a large magnetoresistance, ΔR/R(H=0), of 60% has been observed in thin magnetic films of perovskitelike La-Ba-Mn-O. The films were grown epitaxially on SrTiO₃ substrates by off-axis laser deposition. In the as-deposited state, the Curie temperature and the saturation magnetization were considerably lower compared to bulk samples, but were increased by a subsequent heat treatment. The samples show a drop in the resistivity at the magnetic transition, and the existence of magnetic polarons seems to dominate the electric transport in this region.