Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: Frustrated Magnets - Chiral Magnets & RuCl₃

TT 34.3: Vortrag

Dienstag, 8. März 2016, 14:30–14:45, H20

The microscopic NMR probe in chiral magnets: zero field-, field-modulated- and Skyrmion- states in FeGe and MnSi — •Michael Baenitz¹, Hiroshi Yasuoka¹, Mayukh Majumder¹, Panchanan Khuntia¹, Sebastian Witt², Cornelius Krellner², and Markus Schmidt¹ — ¹MPI for the Chemical Physics of Solids, 01187 Dresden, Germany — ²Goethe University Frankfurt, 60438 Frankfurt am Main, Germany

Cubic FeGe is a prototype B20 chiral magnet (T_c = 280 K) which allows to study chiral correlations directly "on-site" via the⁵⁷Fe nucleus because of its S=1/2 nuclear spin interacting only with the electron spin moment. NMR provides the static and dynamic staggered local magnetization M_Q through the hyperfine field (H_hf) and the spin lattice relaxation rate (SLRR = 1/T₁). Measurements were performed on randomly oriented ⁵⁷Fe enriched FeGe single crystals between 2-300 K. Helical- , conical- and field-polarized-states could be clearly identified and spin dynamics of each phase was investigated. MnSi single crystals and ²⁹Si enriched MnSi polycrystals were studied by ²⁹Si-NMR (S=1/2) in the ordered state (T_c = 29 K) and above. The T- and H- dependence of H_hf and SLRR was investigated in great detail for both FeGe and MnSi.The ²⁹Si-NMR lines in MnSi are narrow and H_hf-values obtained are smaller than in FeGe. Our results are in general accordance with the extended SCR theory for itinerant helical magnets [1], although the theory does not include the symmetry breaking in the B20 structure and the multi-band nature. For FeGe correlations are complex due to its more localized magnetism.

[1] T. Moriya, J. Phys. Soc. Jpn. 40, 933 (1976)