Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 5: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 1 (jointly with MA)
TT 5.11: Vortrag
Montag, 16. März 2015, 12:15–12:30, H 0110
The Cu2+ mineral szenicsite (Cu3(MoO4)(OH)4) - a spin 1/2 J1-J2 chain compound with a spin gap — •Stefan Lebernegg1, Oleg Janson2, Alexander Tsirlin3, and Helge Rosner1 — 1MPI CPfS, Dresden, Germany — 2Institute of Solid State Physics, Vienna University of Technology, Austria — 3National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
Low-dimensional quantum magnets attracted high attention because of their exotic magnetic properties and ground states, representing an unrivaled field for challenging our understanding of collective quantum phenomena. These are governed by a complex interplay of quantum fluctuations, exchange interactions and lattice topology, which might result in magnetic frustration suppressing ordering processes. The simplest example of a frustrated system is the 1D J1-J2 chain with J2 being AFM, where J1 and J2 are nearest- and next-nearest neighbor exchange couplings, respectively. While for an FM J1 several materials have been discovered, for J1 and J2 both being AFM only very few material realizations have been found so far. In this study, we discuss the Cu2+-mineral szenicsite, Cu3(MoO4)(OH)4. A consistent microscopic magnetic model is derived from LSDA+U calculations, which can perfectly reproduce the thermodynamical data. Based on these results, an effective microscopic magnetic model is developed, demonstrating that at low temperatures szenicsite can be described in terms of an AFM J1-J2 chain with evidence for alternating J2 couplings. According to the ratio J2/J1 ∼ 0.5, a small spin gap should be present whose upper limit was estimated with DMRG and ED to be about 2.5 K.