Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 24: Magnetic Materials I
MA 24.1: Vortrag
Mittwoch, 18. März 2015, 09:30–09:45, H 0112
Excitations in the Skyrmion Lattice of the Molecular Magnet GaV4S8 — •Dieter Ehlers1, Vladimir Tsurkan1, Hans-Albrecht Krug von Nidda1, István Kézsmárki2, Ioannis Stasinopoulos3, Dirk Grundler3, and Alois Loidl1 — 1Experimentalphysik V, EKM, Universität Augsburg, 86135 Augsburg — 2Department of Physics, Budapest University of Technology and Economics, 1111 Budapest, Ungarn — 3Physik-Department E10, TU München, 85747 Garching
The magnetic semiconductor GaV4S8 has the so-called lacunar spinel structure which can be derived from the normal spinel structure by removing every second Ga atom. On cooling, a Jahn-Teller instability lowers the symmetry from cubic to trigonal at 44 K, resulting in twinned crystals. Magnetism arises from V4S8 clusters1,2 which carry an effective spin 1/2, and leads, below 13 K, to a complex magnetic phase diagram consisting of cycloidal, skyrmion, and ferromagnetic regions. These are interpreted in terms of a competition of anisotropic exchange coupling as well as Zeeman interactions in the multi-domain phase. Electron spin resonance has been applied to get insight into the magetization dynamics. Fixed frequency measurements prove the assumed anisotropy model and provide information on the interaction strengths. Broadband microwave experiments at low temperatures show excitations at 5 GHz and above 15 GHz, indicating that the ferromagnetic phase is more complex than anticipated so far.
1R. Pocha et al., Chem. Mater. 12 (2000), 2882
2H. Nakamura et al., J. Phys.: Condens. Matter 17 (2005), 6015