Abstract
A-type antiferromagnetic (AF) order with a two-dimensional (2D) ferromagnetic short-range fluctuation was observed in the stoichiometric orthorhombic La 1-x Eu x MnO 3+δ system (0≤x≤1, δ∼0 with trivalent Mn 3+ ). The observation of strong basal plane ferromagnetic coupling of the A-type AF order with fluctuation above antiferromagnetic Néel temperature T N strongly indicates a C-type orbital ordering of e g electrons at higher temperature throughout the whole system. Anomalous decrease of T N from 139 K for LaMnO 3 , to 91 K for La 0.5 Eu 0.5 MnO 3 and down to 42 K for EuMnO 3 is the result of weaker anisotropic superexchange interaction due to stronger Jahn-Teller lattice distortion in orbital-ordered EuMnO 3 from power x-ray Rietveld analysis and Mn K-edge x-ray absorption near-edge structure spectroscopic study.