Eur. Phys. J. B (2013) 86: 68
https://doi.org/10.1140/epjb/e2012-30829-y

Regular Article

Double exchange model for nanoscopic clusters

¹ Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
² Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, 97074 Würzburg, Germany

^a e-mail: angelo.valli@ifp.tuwien.ac.at

Received: 11 September 2012
Received in final form: 12 November 2012
Published online: 25 February 2013

Abstract

We solve the double exchange model on nanoscopic clusters exactly, and specifically consider a six-site benzene-like nanocluster. This simple model is an ideal testbed for studying magnetism in nanoclusters and for validating approximations such as the dynamical mean field theory (DMFT). Non-local correlations arise between neighboring localized spins due to the Hund’s rule coupling, favoring a short-range magnetic order of ferro or antiferromagnetic type. For a geometry with more neighboring sites or a sufficiently strong hybridization between leads and the nanocluster, these non-local correlations are less relevant, and DMFT can be applied reliably.