Role of iso-electronic Ru5+ in thermal transport behavior of YMn1-xRuxO3 compounds

The perovskite manganites compounds with nominal composition YMn1-xRuxO3 (YMRO) (x = 0, 0.05, 0.1 and 0.2) were investigated systematically through structural, morphology and thermal transport measurements. Our thermopower and specific heat measurements indicate that the ground state of rare earth manganite compounds is highly sensitive to the ruthenium (Ru) concentration at Mn-site and henceforth to its cationic radius. These properties were analyzed by considering various models and empirical relations. The high value and complicated temperature dependence of thermopower (S) is an indication of electron-magnon scattering in these systems. The observation of giant suppression in the S with increasing Ruthenium content confirms the mixed-valence subsistence of Mn - Ru network. Specific heat measurements depict an anomaly in the vicinity of TN and associated entropy change, was then obtained by subtracting the lattice part from the experimental data, indicating the existence of magnetic ordering and magnetic inhomogeneity in the samples.