Transport and Magnetic Properties of Nanosized La0.6Sm0.1Sr0.3MnO3 + xCoO Composites

The composites La0.6Sm0.1Sr0.3MnO3 + xCoO (x = 0.0, 0.1, 0.2, 0.3, 0.4 mol), named as Ax samples, were synthesized by the sol-gel technique to derive homogeneous CoO-coated composites. CoO addition induces an increase of resistivity (p) and a decrease of Curie temperature (Tc), magnetization, and Tp at which the p peak is located. It has been concluded that the resistivity below Tp fits well with the equation ρ = ρ0 + ρ2 T2 + ρ4.5T4.5, indicating the importance of grain/domain boundary effects, the electron-electron scattering process, and the two magnon scattering process. On the other hand, the paramagnetic insulating region may be explained by using adiabatic small polaron hopping mechanism, thereby indicating that polaron hopping might be responsible for the conduction mechanism. Magnetoresistance results were explained by a two-level model of tunneling MR and percolation model.