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Evidence of non‐adiabatic small polaron hopping conduction in Bi 0.1 A 0.9 MnO 3 (A = Ca, Sr, Pb)
Author(s) -
Pal Sudipta,
Banerjee Aritra,
Chatterjee P.,
Chaudhuri B. K.
Publication year - 2003
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200301659
Subject(s) - polaron , variable range hopping , ionic radius , condensed matter physics , electrical resistivity and conductivity , doping , conductivity , materials science , magnetoresistance , atmospheric temperature range , analytical chemistry (journal) , chemistry , ion , electron , physics , magnetic field , thermodynamics , organic chemistry , chromatography , quantum mechanics
A detailed study of the electrical transport properties of semiconducting perovskites Bi 0.1 A 0.9 MnO 3 (A = Ca, Sr, Pb of increasing ionic radius r i ) have been made over a wide range of temperature 80–375 K. XRD studies indicate a change of structural differences with change of ionic radius r i of A. The dc conductivity of the Sr‐ and Pb‐doped samples with larger r i is much lower than that of the Ca‐doped sample of smaller r i . Unlike the Sr‐ and Pb‐doped samples, little negative magnetoresistance is also observed in the Ca‐doped sample (below 115 K at 1.5 T field). The resistivity data below θ D /2 ( θ D is the Debye temperature) are fitted well with the Mott's variable range hopping (VRH) model, whereas the nearest‐neighbour small polaron hopping mechanism satisfactorily fitted the high‐temperature (above θ D /2 ≈ 200 K) conductivity data. The condition of the non‐adiabatic small polaron hopping mechanism is valid for all the samples. The estimated electron–phonon interaction constant γ p (= 2 W H / hν ph ) of the highly resistive Sr‐ and Pb‐doped samples are much higher (≫4) than those of the low‐resistive Ca‐doped oxide sample (≈4). Large values of γ p destroy spin ordering in the Sr‐ and Pb‐doped samples, while for the lower value of γ p in the Ca‐doped sample spin ordering favours high conductivity and show a negative magnetoresistance (only in the low‐temperature region). Low‐temperature ( T < θ D /2) frequency‐dependent ac conductivity data indicate that the conduction mechanism in the highly resistive Sr‐ and Pb‐doped samples is primarily due to hopping of Anderson‐localized charge carriers.