Mn and Mg interdiffusion and magnetotransport properties of La0.7Sr0.3MnO3 films on MgO (100) substrate

An anomalous annealing temperature dependence of magnetotransport properties has been observed in sol-gel-derived polycrystalline thin films of La0.7Sr0.3MnO3 (LSMO) on MgO substrate. The resistivity peak temperature (T-p) drops dramatically with increasing annealing temperature, while the peak resistivity rises sharply. The Rutherford backscattering analysis of these films strongly points to the existence of Mn and Mg interdiffusion for samples annealed at temperatures as low as 650 degrees C; this interdiffusion was enhanced with increasing annealing temperature. In order to confirm the effects of interdiffusion, we fabricated epitaxial films with Mn sire substitution by Mg and compared their physical properties with those of polycrystalline films on MgO substrate. It is argued that the observed anomalous annealing temperature dependence arises from a combination of Mn site substitution by Mg and the grain boundary spin-polarized scattering of polycrystalline film on MgO substrate.