CRYSTALLINITY AND MAGNETORESISTANCE IN LA1-XCAXMNO3 THIN-FILMS

The crystallinity of La1-xCaxMnO3 thin films can be controlled by prep aring the films on substrates with different lattice parameters. Close ly lattice matched LCMO thin films on LaAlO3 (LAO) substrates exhibit a high degree of crystallinity and have magnetoresistance (MR) and MR ratio [R(H=0 T)-R(H=6 T)]/R(H=6 T) that is sharply peaked in the vicin ity of the metal-insulator transition temperature (T-MI). Notably, fil ms grown on LAO(011) have T-MI shifted up in temperature similar to 20 K higher than the same films on LAO(001) substrates. LCMO films on Al 2O3 and Y-ZrO2, that are not as closely lattice matched, have a lower degree of crystallinity, less sharply peaked MR and a nearly constant MR ratio below T-MI over a broad temperature range. (C) 1998 American Institute of Physics. [S0021-8979(98)08023-2].