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TT: Fachverband Tiefe Temperaturen

TT 45: Correlated Electrons: Poster Session

TT 45.64: Poster

Donnerstag, 29. März 2012, 15:00–19:00, Poster B

Magnetic ordering transitions of the effective XY-spin-1/2 compound Cs₂CoCl₄ in transverse magnetic fields — •Oliver Breunig¹, Eran Sela², Benjamin Buldmann², Markus Garst², Petra Becker³, Ladislav Bohatý³, Christian Dax¹, Ralf Müller¹, and Thomas Lorenz¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Institut für Theoretische Physik, Universität zu Köln — ³Institut für Kristallographie, Universität zu Köln

Cs₂CoCl₄ is a model system for studying the magnetism of one-dimensional spin chains. It contains CoCl₄ tetrahedra, which form one-dimensional chains along the crystallographic b axis. The orbital groundstate of Co²⁺ is split by the crystal field into doublets and an easy-plane anisotropy of the magnetization is established. The ground-state doublet is separated from the first excited doublet state by approximately 15 K, such that at temperatures between 0.3 and 4 K the compound is well described by the one-dimensional XXZ model. Decreasing temperature further, magnetic order arises at field-dependent temperatures T_C(H). According to [1] spins are confined to the bc-plane in the ordered phase. Measuring thermal expansion with a magnetic field applied along the crystallographic b-axis, we observe a series of magnetic transitions within the ordered state. We discuss thermodynamic properties of the magnetically ordered state.

This work was supported by the DFG through SFB 608.
M. Kenzelmann et al., Phys. Rev. B 65 (2002).