Eur. Phys. J. B 79, 435-441 (2011)
https://doi.org/10.1140/epjb/e2011-10945-0

Optical investigation of LaMnO₃ thin films: a study of the 2-eV band

¹ CNR-SPIN and Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy
² CNR-SPIN and Dipartimento di Scienze Fisiche, Universitá degli Studi Federico II Complesso Universitario di Monte Sant'Angelo via Cinthia, 80126 Napoli, Italy
³ CNR-SPIN and Dipartimento di Fisica E.R. Caianiello, Università di Salerno, via Ponte don Melillo, 84084 Fisciano, Italy

Corresponding author: ^a alessandro.nucara@roma1.infn.it

Received: 2 December 2010
Revised: 11 January 2011
Published online: 9 February 2011

Abstract

We measure the transmittance of LaMnO₃ (LMO) thin films in the spectral range from 10 000 to 38 000 cm^-1 as a function of temperature. The optical conductivity obtained from the transmittance data is decomposed into five Drude-Lorentz contributions: three of them show evident changes below the Néel temperature T_N 140 K. We discuss the band assignment in the framework of the tight-binding and of the orbitally degenerate Hubbard models. Our results ascribe the overall low-frequency spectrum of LMO to charge-transfer mechanisms involving the t_2g and e_g electrons of the Mn ions, without invoking the presence of excitonic contributions. This finding definitely promotes a Mott-Hubbard scenario for LMO and provides an estimate of the Hamiltonian parameters.