Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 55: Correlated Electrons: Low-Dimensional Systems -Materials 2
TT 55.13: Vortrag
Donnerstag, 14. März 2013, 12:45–13:00, H21
Magnetic anisotropies in the Ising spin-chain compound BaCo2V2O8 — •Sandra Niesen, Michael Seher, Gerhard Kolland, Oliver Breunig, and Thomas Lorenz — II. Physikalische Institut, Universität zu Köln
The effective Ising spin 1/2 system BaCo2V2O8 consists of CoO6 octahedra that form screw chains along the crystallographic c axis which are separated by nonmagnetic Ba2+ and V5+ ions. Long-range antiferromagnetic order is observed below TN= 5.5 K in zero magnetic field with the spins aligned along c. Within the tetragonal ab-plane competing exchange interactions are present causing a lower symmetry of the stabilized magnetic structure. Therefore, magnetic domains occur with ferromagnetic alignment of the spins along [100] and an antiferromagnetic one along [010], or vice versa. High resolution zero-field thermal-expansion data show, that the system undergoes a structural transition from tetragonal to orthorombic while entering the Néel phase. Here, the frustration within the ab-plane is lifted by a small orthorhombic splitting (a−b)/(a+b) ≠ 0, that is below the resolution of diffraction techniques. Moreover, detailed investigations of e.g. magnetization, thermal expansion, specific heat, and thermal conductivity reveal an additional magnetic-field anisotropy within the ab-plane. The corresponding phase diagrams for magnetic fields along [100] and [110] will be presented.
This work is supported by the DFG through SFB 608.