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MA: Fachverband Magnetismus

MA 24: Magnetic Materials I

MA 24.1: Talk

Wednesday, March 18, 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 clusters^1,2 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