Colossal thermoelectric power in Gd-Sr manganites

¹ Department of Physics, Cochin University of Science and Technology - Cochin-22, India
² Low temperature division, UGC-DAE Consortium for Scientific Research - Indore, India
³ Physical & Materials Chemistry Division, National Chemical Laboratory - Pune 411008, India
⁴ Institute of Physics, Chemnitz University of Technology - D-09107 Chemnitz, Germany, EU

^a mraiyer@gmail.com

Received: 17 March 2010
Accepted: 1 July 2010

Abstract

Manganites belonging to the series Gd_1−xSr_xMnO₃ (x=0.3, 0.4 and 0.5) were prepared by wet solid-state reaction and their thermoelectric power was evaluated. Thermoelectric power measurements revealed a peak value at ∼40 K. All the samples exhibited a colossal thermopower at ∼40 K and in that Gd_0.5Sr_0.5MnO₃ exhibited a maximum value of ∼35 mV/K, which is the largest reported for these class of materials at this temperature. Temperature-dependent magnetisation measurements showed that the samples exhibit a phase transition from paramagnetic to spin-glass–like state at these temperatures. Plausible mechanisms responsible for the observed colossal thermoelectric power in Gd-Sr manganites are discussed.