Temperature-dependent photoluminescence in La<inf>2/3</inf>Ca <inf>1/3</inf>MnO<inf>3</inf>

Abstract

Visible photoluminescence and its temperature dependence of La 2/3Ca1/3MnO3 in the temperature range 138-293 K were measured. It was observed that the main broad band centered at ∼ 1. 77 eV with the shoulders at ∼ 1.57 and ∼ 1.90 eV existed in the entire temperature range. It can be well fitted by three Gaussian curves B 1, B2 and B3 centered at ∼ 1.52, ∼ 1. 75 and ∼ 1.92 eV, respectively. The intensities of the peak B1 and B2 vary as temperature increases. In the entire temperature range, the intensity of B1 increases with increasing temperature, whereas that of B2 decreases. The photoluminescence mechanisms for La2/3Ca1/3MnO3 are presented based on the electronic structures formed by the interactions among spin, charge and lattice, in which B1 was identified with the charge transfer excitation of an electron from the lower Jahn-Teller split eg level of a Mn 3+ ion to the eg level of an adjacent Mn4+ ion, B2 is assigned to the transition between the spin up and spin down eg bands separated by Hund's coupling energy EJ and B 3 is attributed to the transition, determined by the crystal field energy EC, between a t2g core electron of Mn3+ to the spin up eg bands of Mn4+ by a dipole allowed charge transfer process. © 2004 Elsevier Ltd. All rights reserved.