MAGNETOTRANSPORT PROPERTIES OF BI SUBSTITUTED THIN-FILMS OF LA-CA-MN-O

This letter is on the observation of anisotropic electrical transport and magnetoresistance (MR) in rf sputtered thin films of La0.62Bi0.05C a0.33MnO3 on Si. Films sputtered on (111)Si are polycrystalline, where as textured films with (110) orientation are obtained from (100) Si. B oth films show a reduction in the lattice constant and relatively high Curie temperatures (262-266 K vs 230 K for bulk polycrystals). Althou gh the films have identical magnetic parameters, resistivity rho and M R data for the (110) textured films show the following features indica tive of possible dependence of magneto transport on crystallographic o rientation: (i) a two order of magnitude enhancement in the low temper ature rho value compared to polycrystalline films, (ii) a semiconducto rlike electrical conduction and the absence of any metallic to semicon ductor transition, and (iii) a relatively large MR, as high as 80% at 40 kOe. (C) 1997 American Institute of Physics.