Magnetic and orbital order in overdoped bilayer manganites

¹ Max-Planck-Institut für Physik Komplexer Systeme Nöthnitzer Str. 38, 01187 Dresden, Germany
² Department of Physics & Meteorology and Centre for Theoretical Studies Indian Institute of Technology - Kharagpur 721302, India
³ The Abdus Salam International Centre for Theoretical Physics Strada Costiera 11, 34014 Trieste, Italy

Corresponding authors: tulika@mpipks-dresden.mpg.de arghya@phy.iitkgp.ernet.in

Received: 20 August 2003
Accepted: 6 November 2003

Abstract

The magnetic and orbital orders for the bilayer manganites in the doping region have been investigated from a model that incorporates the two e_g orbitals at each site, the inter-orbital Coulomb interaction and lattice distortions. The usual double exchange operates via the e_g orbitals. It is shown that such a model reproduces much of the phase diagram recently obtained for the bilayer systems in this range of doping. The C-type phase with () spin order seen by Ling et al.  appears as a natural consequence of the layered geometry and is stabilised by the static distortions of the system. The orbital order is shown to drive the magnetic order while the anisotropic hopping across the e_g orbitals, the layered nature of the underlying structure and the associated static distortions largely determine the orbital arrangements.