Lattice distortion modified anisotropic magnetoresistance in epitaxial La_(0.67)Sr_(0.33)MnO_3 thin films

摘要

Effects of lattice distortion on the anisotropic magnetoresistance (AMR) of magnetron sputtered epitaxial La_(0.67)Sr_(0.33)MnO_3 (LSMO) thin films grown on (001)-oriented SrTiO_3 and MgO substrates were investi?gated. Lattice mismatch at the film/substrate interface gives rise to weak and strong lattice distortion of the LSMO/SrTiO_3 and LSMO/MgO films, respectively. The Jahn-Teller electron-phonon coupling in LSMO leads to significant localization of the eg electrons, causing smaller magnetization, lower transition temperatures (T_C T_(mi)) and larger resistivity. Moreover, AMR of the LSMO films show strong correlations with the substrates. Only two-fold symmetric AMR can be observed in the LSMO/SrTiO_3 films. However, the AMR curves ofthe LSMO/MgO system show clear transitions between two- and four-fold symmetry. This behavior is ascribed to the lattice distortion in the LSMO films which enhances the magneto-crystalline anisotropy.