Anisotropic strains and magnetoresistance of La{sub 0.7}Ca{sub 0.3}MnO{sub 3}

Thin films of perovskite manganite La{sub 0.7}Ca{sub 0.3}MnO{sub 3} were grown epitaxially on SrTiO{sub 3}(100), MgO(100) and LaAlO{sub 3}(100) substrates by the pulsed laser deposition method. Microscopic structures of these thin film samples as well as a bulk sample were fully determined by x-ray diffraction measurements. The unit cells of the three films have different shapes, i.e., contracted tetragonal, cubic, and elongated tetragonal for SrTiO{sub 3}, MgO, and LaAlO{sub 3}, respectively, while the unit cell of the bulk is cubic. It is found that the samples with a cubic unit cell show smaller peak magnetoresistance at low fields ({approx_lt}1T) than the noncubic ones do. The present result demonstrates that the magnetoresistance of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} at low fields can be controlled by lattice distortion via externally imposed strains. {copyright} {ital 1997 American Institute of Physics.}