Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 26: Metal-Insulator Transition
TT 26.7: Vortrag
Donnerstag, 29. März 2007, 15:30–15:45, H19
Spin wave dispersion in the helical spin ordered system SrFeO3 and CaFeO3 — •C. Ulrich1, M. Reehuis1,2, G. Khaliullin1, V. Damljanovic1, A. Maljuk1,2, A. Ivanov3, K. Schmalzl3, Ch. Niedermayer4, K. Hradil5, A. Schneidewind5, and B. Keimer1 — 1Max-Planck-Institut FKF, Stuttgart, Germany — 2Hahn-Meitner-Institut, Berlin, Germany — 3Institut Laue-Langevin, Grenoble, France — 4Paul-Scherrer-Institut, Villigen, Switzerland — 5FRM II, München, Germany
One of the most interesting problems in condensed matter physics is the metal-insulator (MI) transition driven by strong electron correlations. The cubic perovskites SrFeO3 and CaFeO3 are isoelectronic to the manganite system and exhibit also colossal magneto resistance effects. But in contrast, the ferrates show a helical instead of a collinear spin structure. Furthermore, perfectly cubic SrFeO3 shows no charge order and is metallic whereas pseudocubic CaFeO3 shows a MI-transition at the charge ordering transition of 290 K. Therefore, both compounds are right at the borderline between itinerant and strongly correlated electron systems. We have determined the static and dynamic spin properties by neutron scattering. The extracted parameters in the spin Hamiltonian are a big step towards the understanding of the mechanisms behind the helical spin order and the charge order in the ferrates.