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TT: Fachverband Tiefe Temperaturen

TT 17: Correlated Electrons: Spin Systems, Itinerant Magnets 2

TT 17.5: Talk

Monday, March 11, 2013, 16:00–16:15, H19

Long-wavelength helimanegtic order and skyrmion lattice phase in Cu₂OSeO₃ — Alfonso Chacon^1,2, •Tim Adams¹, Michael Wagner¹, Andreas Bauer¹, Georg Brandl^1,2, Bjoern Pedersen², Helmuth Berger³, Peter Lemmens⁴, and Christian Pfleiderer¹ — ¹Technische Universität München, Physik-Department E21, D-85748 Garching, Germany — ²Forschungsneutronenquelle Heinz Maier Leibnitz (FRM II), Lichtenbergstr. 1, 85748 Garching, Germany — ³Ecole Polytechnique Federale Lausanne, CH-1015 Lausanne, Switzerland — ⁴Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany

We report a long-wavelength helimagnetic superstructure in bulk samples of the ferrimagnetic insulator Cu₂OSeO₃. The magnetic phase diagram associated with the helimagnetic modulation inferred from small-angle neutron scattering and magnetization measurements includes a skyrmion lattice phase and is strongly reminiscent of MnSi, FeGe, and Fe_1−xCo_xSi, i.e., binary isostructural siblings of Cu₂OSeO₃ that order helimagnetically. The temperature dependence of the specific heat of Cu₂OSeO₃ is characteristic of nearly critical spin fluctuations at the helimagnetic transition. This provides putative evidence for effective spin currents as the origin of enhancements of the magnetodielectric response instead of atomic displacements considered so far.