The superexchange interaction influence on the magnetic ordering in manganites

Abstract

Manganese oxides such as La 1 −x Sr x MnO 3 and La 1− x Ca x MnO 3 have been attracting considerable attention since the discovery of colossal magnetoresistance (CMR). These materials crystallize in the perovskite-type lattice structure where the crystal field breaks the symmetry of the atomic wave function of the manganese d electrons. The energetically lower t 2g levels are occupied by three localized electrons. Due to a strong Hund coupling their spins are aligned, forming a localized corespin with S=3 /2. The electron configuration of the Mn 3 + ions is t 2 g 3 e g 1 , whereas for Mn 4 + ions the e g electron is missing. Due to a hybridization of the e g wave function with the oxygen 2p orbitals, the e g electrons are itinerant and can move from a Mn 3 + ion to a neighboring Mn 4 + via a bridging O 2 − . In this paper, we present the ferromagnetic (FM) properties of the manganites obtained with the Monte Carlo working on a 2D system, using the ferromagnetic Kondo lattice model (FKLM), including the antiferromagnetic (AF) superexchange (SE) interaction. We investigate the spin–spin correlation function dependence with the electron density, the temperature dependence of structure factor, without the SE interactions and finally, the SE interaction influence of the FM ordering.