Direct evidence for double-exchange coupling in - substituted x ,

S. Sundar Manoharan; R. K. Sahu; M. L. Rao; D. Elefant; C. M. Schneider

doi:10.1209/epl/i2002-00216-4

All issues

Volume 59 / No 3 (August 2002)

Europhys. Lett., 59 3 (2002) 451-457

Abstract

Issue		Europhys. Lett. Volume 59, Number 3, August 2002


Page(s)		451 - 457
Section		Condensed matter: electronic structure, electrical, magnetic, and optical properties
DOI		https://doi.org/10.1209/epl/i2002-00216-4
Published online		01 September 2002

Europhys. Lett., 59 (3), pp. 451-457 (2002)

Direct evidence for double-exchange coupling in $\chem{Ru}$ - substituted $\chem{La_{0.7}Pb_{0.3}Mn}$ $_{1-x}$ $\chem{Ru}$ _x $\chem{O_3}$ , $0.0\leq x \leq 0.4$

S. Sundar Manoharan¹, R. K. Sahu¹, M. L. Rao¹, D. Elefant² and C. M. Schneider²

¹ Materials Chemistry Lab, Department of Chemistry Indian Institute of Technology - Kanpur 208 016 India
² Institute for Solid State Research - 20 Helmholtz Straße D-01069, Dresden, Germany

Corresponding author: ssundar@iitk.ac.in

Received: 7 January 2002
Accepted: 8 May 2002

Abstract

The $\chem{La_{0.7}Pb_{0.3}Mn}$ $_{1-x}$ $\chem{Ru}$ _x $\chem{O_3}$ $(0.0\leq x \leq 0.4)$ system shows an innate relationship between $\chem{Mn}$ and $\chem{Ru}$ ions by a unique double-exchange–mediated transport behavior. This is exonerated by the coexistence of $T_\ab{p}$ and $T_\ab{c}$ (range 330 $\un{K}$ –245 $\un{K}$ for $0.0\leq x \leq 0.4)$ . For $\chem{Ru > 30}$ %, the hole carrier mass influences the transport property. X-ray absorption spectra suggest that the $T_\ab{c}$ - $T_\ab{p}$ match is due to the transport mediated by the $\chem{Mn^{3+}/Mn^{4+}\leftrightarrow Ru^{4+}/Ru^{5+}}$ redox pair and also due to the broad low-spin $\chem{Ru}$ :4d conduction band. For x>0.2, $T<0.5T_\ab{c}$ obeys a modified variable-range hopping model, where $kT_0\propto(M/M_\ab{s})^2$ , suggesting a random magnetic potential which localizes the charge carriers.

PACS: 75.50.Pp – Magnetic semiconductors / 75.30.Vn – Colossal magnetoresistance / 75.30.Et – Exchange and superexchange interactions

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