Panwar, Neeraj and Rao, Ashok and Singh, R. S. and Syu, W. K. and Kaurav, N. and Kuo, Y. K. and Agarwal, S. K.
(2008)
Magnetotransport, thermoelectric power, thermal conductivity and specific heat of Pr2/3Sr1/3MnO3 manganite.
Journal of Applied Physics, 104 (8).
083906-1-083906-6.
ISSN 1089-7550
Abstract
Magnetotransport and thermal studies of Pr2/3Sr1/3MnO3 polycrystalline sintered bulk sample are reported here. The resistivity �(T) and thermoelectric power S(T) data show an insulator to metal (I-M) phase transition at TP≈294 K and TS≈290 K, respectively. Magnetization measurement confirms that the sample undergoes a transition from paramagnetic to ferromagnetic phase at a defined Curie temperature TC=280 K. A substantial increase in magnetoresistance from 2.5% at 280 K to 5% at 77 K has been noticed in a low magnetic field 0.15 T. Small polaron hopping model is found to be operative above the transition temperature TP, whereas electron-electron and electron-magnon scattering processes govern the low temperature metallic behavior. A detailed analysis of thermoelectric power in the ferromagnetic regime suggests that the complicated temperature dependence of S may be understood on the basis of electron-magnon scattering. A transition from decreasing high temperature thermal conductivity (due to local anharmonic distortions associated with small polarons), to an increasing thermal conductivity (due to decreasing of phonon-phonon scattering) and thereafter a peak at ∼100 K (signifying a crossover from Umklapp to defect-limited scattering) have also been noticed. Specific heat measurements depict a pronounced anomaly near the TC, indicating the magnetic ordering and magnetic inhomogeneity in the sample.
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