EFFECT OF INPLANE EPITAXY ON MAGNETOTRANSPORT PROPERTIES OF (LA0.5SR0.5)COO3 THIN-FILMS

We have systematically studied the temperature- and magnetic field-dep endent resistance in (La0.5Sr0.5)CoO3 (LSCO) films with various degree s of in-plane texturing using the biaxially oriented LSCO on CeO2/YSZ/ SiO2/Si substrates. We find that the ferromagnetic transition temperat ure, T-c, is much the same in all samples while the resistive transiti on exhibits metallic behavior (dR/dT > 0) in the epitaxial LSCO to sem iconducting behavior (dR/dT < 0) in the poorly textured LSCO. The magn etoresistance (MR) in the epitaxial LSCO on a LaAlO3 substrate display s two distinct regions; the low field hysteretic MR related to the mag netization hysteresis and the high field linear negative MR due to the suppression of spin fluctuations. In contrast, the MR in the biaxiall y textured LSCO sample shows only the hysteretic behaviors at low fiel ds and no linear MR at high fields. Compared to the polycrystalline-do ped LaMnO3 which shows an enhanced MR at low fields, the MR in the bia xially oriented LSCO does not exhibit such characteristics. We attribu te this to the differences in the spin polarization between LSCO and t he doped LaMnO3. (C) 1998 American Institute of Physics. [S0003-6951(9 8)03931-X].