Grain boundary effects on transport in metalorganic chemical vapor deposition-grown, Ca-doped lanthanum manganites

The transport properties of metalorganic chemical vapor deposited films of lanthanum manganite grown on various substrates are investigated, The more disordered films show a magnetoresistance that is both large and relatively temperature independent over a wide temperature range. At low magnetic fie lds, a linear field dependence is observed and is attributed to spin-polari zed intergrain tunneling. In addition, at low fields a hysteretic dependenc e of resistivity on the magnetic field has been observed. This effect has b een attributed to the scattering of spin-polarized carriers at the grain bo undary. (C) 1998 American Institute of Physics. [S0021-8979(98)18011-8].