The grain growth dependence of the microstructure, and its effects upon magnetic and transport properties were studied in polycrystalline La0.67Ba0.33MnO3. It was found that lateral growth along a certain direction, and a concentric terrace pattern along 3 orthogonal axes, occurred in samples sintered at 1573 and 1673K, respectively. A lamella-like twin microstructure formed in the concentric terrace growth pattern, and the magnetoresistance properties could be enhanced by the twin microstructure. This suggested that the twin boundaries in twin-grains might induce a spin-dependent scattering of electrons that was field-reduced, or a spin-polarized tunneling of electrons that was field-enhanced; thus strengthening the effect of the grain boundaries.

Twin-Microstructure Enhanced Magnetoresistance in La0.67Ba0.33MnO3 Oxides. Y.B.Zhang, S.Li, C.Q.Sun, T.Sritharan: Solid State Communications, 2006, 139[10], 506-10