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Title: Colossal thermoelectric power in charge ordered lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3})

Lanthanum calcium manganites (La{sub 0.5}Ca{sub 0.5}MnO{sub 3}) with a composition close to charge ordering, synthesized by high energy ball milling, was found to exhibit colossal thermoelectric power. Thermoelectric power (TEP) data was systematically analyzed by dividing the entire temperature range (5 K–300 K) into three different regimes to explore different scattering mechanisms involved. Mandal's model has been applied to explain TEP data in the region below the Curie temperature (T{sub C}). It has been found that the variation of thermoelectric power with temperature is pronounced when the system enters the charge ordered region at T < 200 K. For temperatures lower than 120 K, due to the co-existence of charge ordered state with a spin-glass state, the variation of thermoelectric power is maximum and exhibited a peak value of −80 mV/K at 58 K. This has been explained by incorporating Kondo properties of the spin-glass along with magnon scattering. FC-ZFC magnetization measurements indicate the existence of a glassy state in the region corresponding to a maximum value of thermoelectric power. Phonon drag contribution instead of spin-glass contribution is taken into account to explain TEP in the region 120 K < T < T{sub C}. Mott's polaronic contribution of charge carriers are considered to interpret TEP in the high temperature region (T > T{sub C}). Themore » optimal Mn{sup 4+}-Mn{sup 3+} concentration in charge ordered La{sub 0.5}Ca{sub 0.5}MnO{sub 3} was examined by X-ray Photoelectron Spectroscopy analysis which confirms the charge ordered nature of this compound.« less
Authors:
;  [1] ; ;  [2] ;  [3] ;  [4] ; ;  [5]
  1. Department of Physics, Cochin University of Science and Technology, Cochin 682022 (India)
  2. Low temperature division, UGC-DAE Consortium for Scientific Research, Indore (India)
  3. Material Science and Technology Division, National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram–695019 (India)
  4. Department of Physics, Sultan Qaboos University, Muscat PC 123, Sultanate of Oman (Oman)
  5. Institute of Physics, University of Augsburg, Augsburg 86135 (Germany)
Publication Date:
OSTI Identifier:
22402716
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CALCIUM; CURIE POINT; LANTHANUM; MAGNETIZATION; MANGANESE IONS; MILLING; PHONONS; SCATTERING; SPIN GLASS STATE; TEMPERATURE RANGE 0065-0273 K; X-RAY PHOTOELECTRON SPECTROSCOPY