Dresden 2006 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.92: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Magnetic excitations in charge and orbital ordered manganites — •D. Senff¹, M. Benomar¹, O. Schumann¹, F. Krüger², S. Scheidl², Y. Sidis³, A. Revcolevschi⁴ und M. Braden¹ — ¹II. Physikalisches Institut, Universität zu Köln, Germany — ²Institut für Theoretische Physik, Universität zu Köln, Germany — ³Laboratoire Léon Brillouin, France — ⁴Laboratoire de Physico-Chimie de l’Etat Solide, Université Paris Sud, France

Charge and orbital ordering around half doping is a unique feature in the physics of manganite-oxides and the competition of these insulating phases with FM metallic phases seems to be the origin of the well known colossal magnetoresistance in perovskite manganites. We present the magnetic excitation spectrum within the charge and orbital ordered state of single layered La_0.5Sr_1.5MnO₄, a compound which exhibits a very stable CE-type AFM ordering.

Using inelastic neutron scattering techniques we determined the complete spin-wave dispersion of the CE-phase. At low temperatures the main features of the excitation spectrum is a steep dispersion along the FM exchange pathways of the CE-type structure, while the dispersion in the perpendicular directions exhibits only a very narrow bandwidth. Within linear spin-wave theory we model the observed data and conclude that the FM interaction is the most dominant magnetic energy in the AFM CE-type ordering scheme. This interpretation is confirmed by the excitation spectrum and the quasielastic diffuse magnetic scattering at temperatures well above T_N which both give clear evidence for short-range ferromagnetic correlations.