Eur. Phys. J. B 10, 397-408 (1999)
https://doi.org/10.1007/s100510050869

Charge ordering-disordering in the Th-doped CaMnO₃

¹ Laboratoire CRISMAT (UMR 6508 associée au CNRS) , ISMRA et Université de Caen, 6 boulevard du Maréchal Juin, 14050 Caen Cedex, France
² EMAT, University of Antwerp (RUCA), Groenenborgerlaan 171, 2020 Antwerp, Belgium

Corresponding author: ^a hervieu@crismat.ismra.fr

Received: 2 November 1998
Published online: 15 August 1999

Abstract

The structural transitions that appear in the manganites Ca1-xTh_xMnO₃ versus temperature are studied in connection with their magnetic and transport properties, and compared to those of the Ca1-xLn_xMnO₃ manganites. An orthorhombic to monoclinic transition is observed for low x values (I≈0.08); this structural distortion, also observed for Ln-doped oxides, is related to the magnetoresistance properties. For higher x values (0.15≤x≤0.30), modulated commensurate and incommensurate phases are obtained at low temperature, with a=1/_qap√2, b=2_ap and c=a_p√2, which are related to Mn³⁺/Mn⁴⁺ charge ordering (CO) phenomena. T_CO 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 (x≈0.25-0.30) not seen for Ca1-xSm_xMnO₃ phases (x≈0.50-0.60).