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Study of the percolative nature of thermoelectric power and resistivity in Pr0.66R0.04Sr0.3MnO3 (R = Tb, Y, Ho and Er) manganites.

Published online by Cambridge University Press:  01 February 2011

N. Rama ,
V. Sankaranarayanan  and
M.S.R. Rao
N. Rama
Affiliation:
Department of Physics and (IIT) Madras, Chennai - 600 036., India Materials Science Research Centre, Indian Institute of Technology, (IIT) Madras, Chennai - 600 036., India.
V. Sankaranarayanan
Affiliation:
Department of Physics and (IIT) Madras, Chennai - 600 036., India
M.S.R. Rao*
Affiliation:
Department of Physics and (IIT) Madras, Chennai - 600 036., India Materials Science Research Centre, Indian Institute of Technology, (IIT) Madras, Chennai - 600 036., India.
*
*msrrao@iitm.ac.in
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Abstract

We have studied the resistivity and thermoelectric power of Pr0.66R0.04Sr0.3MnO3 where R = Tb, Y, Ho and Er and have analyzed it within a percolative framework. Both resistivity and thermoelectric power quantities were found to show a strong dependence on the disorder (<σ>2) with the high temperature activation energy in both increasing as <σ>2 is increased, implying that as the disorder increases, carriers get more localized. The percolative nature of the thermopower was analyzed assuming that the lattice has coexisting metallic (Smet) and insulating (Sins) components above and below the Curie temperature (TC) which are independent of each other. Hence total S(T) = pSmet(T) + (1-p)Sins with the volume metallic fraction p=1/(1+exp(-Uo(1-T/TC)/kBT) [1]. A similar analysis was done using the resistivity data. It was seen that the TC from both thermopower and resistivity fits were nearly the same indicating that they have a common origin. This analysis clearly proves that the metal insulator transition in manganites is percolative in nature and that the transport properties show a strong percolation tendency.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 848: Symposium FF – Solid-State Chemistry of Inorganic Materials V , 2004 , FF9.22
Copyright
Copyright © Materials Research Society 2005

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References

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