Charge ordering-disordering in the Th-doped CaMnO3 |
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Authors: | M Hervieu C Martin A Maignan G Van Tendeloo B Raveau |
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Institution: | (1) Laboratoire CRISMAT (UMR 6508 associée au CNRS), ISMRA et Université de Caen, 6 boulevard du Maréchal Juin, 14050 Caen Cedex, France, FR;(2) EMAT, University of Antwerp (RUCA), Groenenborgerlaan 171, 2020 Antwerp, Belgium, BE |
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Abstract: | The structural transitions that appear in the manganites Ca1-xThxMnO3
versus temperature are studied in connection with their magnetic and transport properties, and compared to those of the Ca1-xLnxMnO3 manganites. An orthorhombic to monoclinic transition is observed for low x values (;this structural distortion, also observed for Ln-doped oxides, is related to the magnetoresistance properties. For higher
x values (), modulated commensurate and incommensurate phases are obtained at low temperature, with , b
=2
a
p and , which are related to Mn3+/Mn4+ charge ordering (CO) phenomena. T values, determined from electron diffraction, are in agreement with those determined from the M
(
T
) curves. The low temperature electron microscopy shows that the CO in those oxides is more complex than in Ln-doped manganites.
In particular, the destabilisation of CO and consequently of the antiferromagnetic interactions is evidenced as the thorium
content increases which may explain the appearance of a spin-glass like behavior for higher x values not seen for Ca1-xSmxMnO3 phases .
Received 2 November 1998 |
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Keywords: | PACS 61 14 -x Electron diffraction and scattering - 75 30 -m Intrinsic properties of magnetically ordered materials - 72 20 My Galvanomagnetic and other magnetotransport effects |
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