Europhys. Lett.
Volume 65, Number 2, January 2004
Page(s) 262 - 268
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 January 2004
Europhys. Lett., 65 (2) , pp. 262-268 (2004)
DOI: 10.1209/epl/i2003-10067-5

Magnetic and orbital order in overdoped bilayer manganites

Tulika Maitra1 and A. Taraphder2, 3

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

(Received 20 August 2003; accepted 6 November 2003)

The magnetic and orbital orders for the bilayer manganites in the doping region 0.5<x<1.0 have been investigated from a model that incorporates the two eg orbitals at each $\chem{Mn}$ site, the inter-orbital Coulomb interaction and lattice distortions. The usual double exchange operates via the eg 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 ( $\pi,0,\pi$) 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 eg orbitals, the layered nature of the underlying structure and the associated static distortions largely determine the orbital arrangements.

75.47.Gk - Colossal magnetoresistance.
75.30.Et - Exchange and superexchange interactions.

© EDP Sciences 2004