Structural and transport properties of Bi-substituted Co2MnO4

We report the structural and transport properties of the Bi-substituted Co2MnO4 multiferroic materials. Samples synthesized using the solid state reaction route with the composition BixCo2-xMnO4 (<0x<0.3) exhibit a single phase behavior with a cubic spinel structure (space group Fd3m). The lattice parameter was found to increase with the Bi substitution. The dc-conductivity studies reveal that all the samples possess a semiconducting behavior. The resistivity was found to decrease with the increase in the Bi substitution. The dc- as well as ac-conductivity data were analyzed in the light of various conduction models. The dc-conductivity data are explained using the variable range hopping model. The ac conductivity calculated from the dielectric data as a function of temperature and frequency demonstrates the cross over from small polaron tunneling to correlated barrier hopping type conduction in these materials. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3067635]