Abstract:
Earlier we observed colossal thermoelectric power in charge ordered intermediate band width
manganite La0.5Ca0.5MnO3 and was explained based on charge ordering and occurrence of spin glass
states. With a view to extending such a study on small band width Gd-Sr manganites, both unmilled
and milled forms of Gd1−xSrxMnO3 (x = 0.3, 0.5, and 0.6) samples were prepared. Nano forms of Gd1
−xSrxMnO3were prepared by high energy ball milling. All compositions, both milled and unmilled
forms, exhibited colossal thermoelectric power. The absolute value of thermoelectric power almost
doubled in the case of milled samples and attained a maximum value of −69 mV K−1 at 42 K, where a
spin glass transition takes place. In order to explain the occurrence of transition at∼42 K, field cooling
and zero-field cooling magnetic measurements were conducted and we found that the peak value of
thermoelectric power is observed at the same magnetic ordering temperature. The results are further
modelled using Mandal’s model by incorporating Kondo properties of spin glass along with magnon
scattering.
