A study was made of the effect of grain boundaries upon the transport properties and upon the local magnetization orientation. Thin films of perovskite-related La2/3Ca1/3MnO3 were deposited onto bicrystal substrates by using pulsed laser deposition. Transport measurements revealed an enhancement of the magnetoresistance across the grain boundary. The structure of the boundary was evaluated by means of electron microscopy. It was found that, unlike the tortuous boundaries which were typical of bicrystals of high-temperature superconductors, the boundaries in these films were relatively straight and well-defined. However, magneto-optical imaging showed that the local magnetization was directed out of the plane at the grain boundary, but lay within the plane of the grains on either side. This coordinated reorientation of local magnetization near to the grain boundary led to an enhanced magnetoresistance across the boundary in low fields.

Grain Boundary Structures in (La,Ca)MnO3 Thin Films. D.J.Miller, Y.K.Lin, V.Vlasko-Vlasov, U.Welp: Journal of Applied Physics, 2000, 87[9], 6758-60