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Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 44: Poster Session Correlated Electrons

TT 44.80: Poster

Thursday, March 17, 2011, 10:00–13:00, P1

Dynamic triple-helix spin clusters in the paramagnetic phase of MnSi — •A. Hamann1, D. Lamago2, Th. Wolf1, H. v. Löhneysen1, and D. Reznik31Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany — 2Laboratoire Léon Brillouin, CEA Saclay, France — 3Department of Physics, University of Colorado, Boulder, USA

MnSi exhibits helical magnetic order at low temperatures and ambient pressure with underlying Fermi-liquid (FL) properties. At high pressures an exotic magnetic state forms referred to as partial order [1], where the helical propagation vector becomes disordered. Non-FL temperature dependence of the electrical resistivity appears nearby in the phase diagram. Our numerical calculations show that isotropic nearest-neighbor spin interactions in MnSi favor a glassy aggregation of topological magnetic clusters that we call triple-helices. They are similar to double helices well known from blue phases of liquid crystals [2] and have the spectral signature of partial order. Their stability increases as their size decreases. This model may explain most of the puzzling properties of MnSi including the non-FL behavior and the two-component phase transition that was revealed by specific heat [3]. Our detailed neutron scattering measurements in the paramagnetic phase where temperature sets the scale of the size of dynamic spin clusters fully confirm this picture.
C. Pfleiderer, D. Reznik et al., Nature 427, 227 (2004)
D. C. Wright and N. D. Mermin, Rev. Mod. Phys. 61, 385 (1989)
D. Lamago et al., Physica B 385-386, 385 (2006)

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