Effects of Mn doping on the normal-state transport of tetragonal FeSe superconductor up to 700 K
Department of Physics, National Changhua University of Education - Changhua 500, Taiwan
Received: 24 July 2014
Accepted: 17 September 2014
A series of Fe1−xMnxSe polycrystalline samples with , 0.02, 0.05 and 0.08 is prepared by conventional solid-state reaction. Normal-state transport of electrical resistivity and thermopower are investigated up to 700 K. The electrical resistivity monotonically increases with increasing Mn content. The temperature dependence of resistivity is analyzed using a power-law equation . At , the electrical resistivity behavior resembles misfit-layered cobalt oxides Ca3Co4O9+δ. The electrical resistivity follows a T2-dependence between 150 and 220 K with the Fermi-liquid transport coefficient having the size between and , followed by a transition to an incoherent metal in the vicinity of Mott transition. Metal-nonmetal transition is observed at 315 K, 370 K, 304 K and 275 K for , 0.02, 0.05 and , respectively. The resistivity follows a power law for , which might comply with the prediction of the spin fluctuation theories for the behavior in the vicinity of an antiferromagnetic transition. Thermopower exhibits unconventional behavior. Above room temperature, the thermopower shows a sign crossover to positive at 352 K, 537 K, and 374 K for , 0.05, and 0.08, respectively. Unlike the undoped and Bi-doped FeSe, the thermopower of Mn-doped samples increases with increasing temperature in the high-temperature regime up to 700 K, which might arise from the thermally activated conduction of hole carriers. Being consistent with earlier reports, the sharp dip anomaly of thermopower occurs between 100 and 120 K and seems to be associated with the excitations of a pseudogap ground state.
PACS: 74.25.F- – Transport properties / 74.62.Dh – Effects of crystal defects, doping and substitution / 74.70.-b – Superconducting materials other than cuprates
© EPLA, 2014