Magnetic and electrical transport properties of La0.67Ca0.33MnO3 (LCMO):: xSiCN composites

The magnetic and electrical transport properties of La0.67Ca0.33MnO3 (LCMO): xSiCN (x=0-40 vol %) composites, synthesized by mechanical mixing of citrate gel derived LCMO and polymer derived ceramics SiCN, have been investigated as a function of composition. The ability of SiCN to behave as a sintering additive leads to interesting magnetic and electrical properties. Si+4, being strongly favored for tetrahedral coordination, cannot enter the perovskite lattice. Saturation moment, M-S of 68 emu/gm at 5 K and at 5 kOe field of pure LCMO shifts to 79 emu/gm in the sample with x=0.05 and then decreases monotonically as x increases further. The lower M-S, T-C and high electrical resistivity of the sample with x=0, compared to those which have been reported in the literature, is due to small particle size in nm range. SiCN as a sintering aid increases the particle size of LCMO to 1-2 mum for x=0.10. Three orders of magnitude change in electrical resistivity (204 Omega cm for x=0;0.5 Omega cm for x=0.05) is explained on the basis of the difference in the mobility of the charge carriers, by fitting the experimental transport data with a correlated polaron hopping model. (C) 2004 American Institute of Physics.