ANISOTROPIC STRAIN AND MAGNETORESISTANCE OF LA0.7CA0.3MNO3

Thin films of perovskite manganite La0.7Ca0.3MnO3 were grown epitaxial ly on SrTiO3(100), MgO(100) and LaAlO3(100) substrates by the pulsed l aser deposition method. Microscopic structures of these thin film samp les as well as a bulk sample were fully determined by x-ray diffractio n measurements. The unit cells of the three films have different shape s, i.e., contracted tetragonal, cubic, and elongated tetragonal for Sr TiO3, MgO, and LaAlO3, respectively, while the unit cell of the bulk i s cubic. It is found that the samples with a cubic unit cell show smal ler peak magnetoresistance at low fields (less than or similar to 1 T) than the noncubic ones do. The present result demonstrates that the m agnetoresistance of La0.7Ca0.3MnO3 at low fields can be controlled by lattice distortion via externally imposed strains. (C) 1997 American I nstitute of Physics.