Abstract
Magnetic, structural and Mn K-edge X-ray absorption near-edge structure (XANES) spectroscopic studies have been made on the stoichiometric Lai <sub>1-x</sub> Eu <sub>x</sub> MnO <sub>3</sub> (0≤x≤ 1) system with trivalent Mn <sup>3+</sup> . The system undergoes an A-type antiferromagnetic (AF) order with Néel temperature TN ranging from 139 K for LaMnO <sub>3</sub> to 42 K for smaller EuMnO <sub>3</sub> , above which a two-dimensional ferromagnetic (2D-FM) short range fluctuation prevails with T <sub>2D</sub> > T <sub>N</sub> at low applied field. This is the result of anisotropic superexchange interaction for the A-type AF order with strong basal plane FM coupling of the orbital-ordered e <sub>g</sub> electrons and weak c-axis AF coupling of t <sub>2g</sub> electrons. The anomalous decrease of T <sub>N</sub> with increasing smaller Eu substitution is due to more localized t <sub>2g</sub> electrons from a stronger crystal field splitting and lattice distortion in the MnO <sub>6</sub> octahedron. Both T <sub>2D</sub> and T <sub>N</sub> are field dependent and nearly merge at higher applied fields. © 2004 Elsevier B.V. All rights reserved.