Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Postersession Correlated Electrons: Metal Insulator Transition, Spin Systems and Itinerant Magnets
TT 33.11: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Investigation of Orbital-Ordering in Sr2VO4 — •Joseph M. Law1, 2, Eva Brücher1, Sukanta Karmakar1, Karl Syassen1, and Reinhard K. Kremer1 — 1Max Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany — 2Dep. of Physics, Loughborough University, Loughborough, U.K.
Sr2VO4 is a Mott insulator which crystallizes with the tetragonal K2NiF4 structure. It hosts V4+, (3d1 configuration), is another layered S=1/2 afm with unusual ground state properties. Recently it was shown that tetragonal Sr2VO4 undergoes a phase transition (PT) near 104K evidenced by a sudden drop of the magnetic susceptibility and anomalies in the lattice parameters (c increases by 0.15%) but no change of the crystallographic symmetry. Based on ab initio calculations the PT was ascribed to an orbital-ordering transition which leads to a decreasing occupancy of the dxy orbital balanced by an increasing electronic density along the c axis.[1] We have investigated the orbital-ordering PT by heat capacity, dc resistivity and dielectric measurements on polycrystalline samples of tetragonal Sr2VO4. The heat capacity measurements display an anomaly confirming a PT at 104 K. Additionally, a sluggish precursor regime extending up to 125K consistent with the lattice properties was found. Our resistivity and dielectric measurements prove a Mott gap of ∼ 100 meV as already seen in thin films, which reveals an increase of the activation energy below ∼ 125 K leading to a rapid growth of the electrical resistance below the PT.
[1] H. D. Zhou et al., Phys. Rev. Lett. 99, 136403 (2007).