Magnetoresistance and thermoelectric transport in EuTi1-xNbxO3

Abstract We report the impact of Nb substitution in EuTi 1- x Nb x O 3 ( x  = 0, 0.01, 0.03, 0.06 and 0.1) on the magnetization, resistivity, magnetoresistance ( MR ), thermopower (S) and thermal conductivity ( κ ) over a wide temperature range ( T  = 390–2.5 K). Partial replacement of Ti by Nb weakens the antiferromagnetic coupling between Eu-4 f spins, drastically reduces low-temperature resistivity and induces insulator-metal transition above the Neel temperature. MR is negative and decreases from 20% for x  = 0.01–0.5% for x  = 0.1 at 2.5 K but the sign of MR changes to positive at higher temperatures for x  = 0.06 and 0.1. The negative MR is suggested due to spin-dependent scattering of Ti-3d conduction electrons by localized Eu-4 f spins and we fitted the experimental data to a theoretical model. The negative sign of S asserts electron doping. The values of S and κ systematically decrease with increasing Nb content. κ( T ) is analyzed using the Debye-Callaway model.