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Mixed mode electrical transport behavior in nanocrystalline La–Ca‐Manganite synthesized by microwave refluxing
Author(s) -
Nayak Bibhuti B.,
Vitta Satish,
Bahadur D.
Publication year - 2005
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200521247
Subject(s) - manganite , nanocrystalline material , magnetoresistance , orthorhombic crystal system , materials science , annealing (glass) , microstructure , electrical resistivity and conductivity , atmospheric temperature range , microwave , grain boundary , grain size , chemical engineering , analytical chemistry (journal) , nanotechnology , chemistry , crystallography , metallurgy , condensed matter physics , crystal structure , ferromagnetism , thermodynamics , magnetic field , electrical engineering , organic chemistry , physics , engineering , quantum mechanics
Abstract Nanocrystalline La 0.67 Ca 0.33 MnO 3 powders were prepared from organic precursors using a microwave synthesis technique. A variation of the precursor solution pH and annealing temperature was found to change the effective Mn 4+ concentration which leads to variations in electronic behavior. In all the cases however, a single phase microstructure was observed showing the stability of orthorhombic manganite. The nanocrystalline manganite prepared from a solution with a pH of 10.5 has the lowest Mn 4+ and accordingly low electrical and magnetic transition temperatures. The electrical transport behavior of powders prepared from precursor solutions with pH of 11.5 and 12.5 could be modeled using an effective medium approach across the whole temperature range, 30 K to 300 K. The magnetoresistance in these nanocrystalline manganites increases with decreasing temperature, an effect of increased grain boundaries. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)