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. Reznik3 — 1Karlsruhe 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.
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D. C. Wright and N. D. Mermin, Rev. Mod. Phys. 61, 385 (1989)
D. Lamago et al., Physica B 385-386, 385 (2006)