Berlin 2015 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 30: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 3 (jointly with MA)
TT 30.2: Vortrag
Dienstag, 17. März 2015, 09:45–10:00, H 0110
Magnetism of the effective spin-1/2 compound Cs2CoCl4 — •Oliver Breunig1, Markus Garst2, Eran Sela2, Achim Rosch3, Benjamin Buldmann3, Petra Becker4, Ladislav Bohatý4, Ralf Müller1, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln — 2Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University — 3Institut für Theoretische Physik, Universität zu Köln — 4Institut für Kristallographie, Universität zu Köln
Cs2CoCl4 contains CoCl4 tetrahedra, which form one-dimensional chains along the crystallographic b axis. The orbital groundstate of Co2+ (3d7, S=3/2) is split by a crystal field anisotropy D into two doublets and an easy-plane anisotropy of the magnetization is established. We measured specific heat and thermal expansion at temperatures down to 50 mK and in magnetic fields applied along different crystallographic axes. At temperatures between 0.3 and 4 K a description as an effective spin-1/2 XXZ chain arises. By considering both, thermal as well as virtual excitations of higher crystal field states, we find that the spin chain is in the XY-limit with an anisotropy Jz/J⊥≈ 0.12 substantially smaller than previously believed. Magnetic order arises at a field-dependent temperature TC(H) due to inter-chain couplings which form a frustrated triangular lattice. Depending on the orientation of the magnetic field we observe various ordered phases. We present phase diagrams for different field directions and discuss the origin of the phases.