Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons: Spin Systems and Itinerant Magnets - Frustrated Magnets II
TT 20.2: Vortrag
Montag, 31. März 2014, 15:15–15:30, HSZ 304
Magnetic anisotropies in the Ising spin-chain compound BaCo2V2O8 and the effect of substitution — •Sandra Niesen1, Gerhard Kolland1, Michael Seher1, Oliver Breunig1, Martin Valldor1, Markus Braden1, Beatrice Grenier2, and Thomas Lorenz1 — 1II. Phys. Institut, Universität zu Köln — 2SPSMS, CEA-INAC/UJF-Grenoble, France
The effective Ising spin-1/2 system BaCo2V2O8 consists of CoO6 octahedra that form screw chains along the c axis. Long-range antiferromagnetic order is observed below TN= 5.5 K in zero magnetic field with the spins aligned along c. Within the ab plane the spin arrangement is known to be frustrated with a ferromagnetic alignment of neighbouring spins along [100] and an antiferromagnetic one along [010]. Our zero field thermal expansion data show that the Néel order is accompanied by a structural transition from tetragonal to orthorhombic, which lifts the magnetic frustration [1]. Consequently, the magnetic-field influence is anisotropic within the ab plane as seen in, e.g. measurements of the magnetization, thermal expansion, specific heat, and thermal conductivity. A detailed study of this anisotropy and the resulting magnetic phase diagrams will be presented. In addition, we will discuss the influence of partial substitution of Ba by Sr and of Co by either magnetic or nonmagnetic ions.
This work has been supported by the DFG via SFB 608 and through the Institutional Strategy of the University of Cologne within the German Excellence Initiative.
[1] S. Niesen et al., PRB 87, 224413 (2013)