Magnetotransport properties of La0.7Ca0.3MnO3 thick films prepared by spray pyrolysis

A spray pyrolysis deposition technique has been used to prepare: thick films of half-metallic ferromagnet La0.7Ca0.3MnO3 on LaAlO3 (001) and yttria-stabilized zirconia Y-ZrO2 (100) single-crystal substrates. The films deposited on LaAlO3 (001) exhibited a high degree of crystallinity with both in-plane and out-of-plane texture and a very sharp insulator to metal transition at T-IM = 270 K. The intrinsic magnetoresistance (MR) reaches 70% at T-IM in 3 T, a similar value as in the bulk material of the same composition. The extrinsic intergrain MR, however, is only 0.5% at 40 K in 3 T, 50 times smaller than for the bulk. By contrast, films grown on YSZ single crystals have a broad insulator to metal transition at a lower T-IM of approximately 220 K and poor intrinsic MR. They show however an extrinsic MR as large as in the bulk. The extrinsic MR is interpreted as arising from crystalline and magnetic disorder at the grain boundaries.