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TT: Fachverband Tiefe Temperaturen

TT 70: Correlated Electrons: Spin Systems and Itinerant Magnets – Chiral Magnets (jointly with MA)

TT 70.3: Vortrag

Mittwoch, 18. März 2015, 18:30–18:45, H 3005

NMR-on site-probe of field-modulated and Skyrmion states in chiral magnets: FeGe and Cu₂OSeO₃ — •Michael Baenitz, Mayukh Majumder, Panchanan Khuntia, Hiroshi Yasuoka, and Markus Schmidt — MPI for the Chemical Physics of Solids, 01187 Dresden, Germany

Cubic FeGe is a prototype B20 chiral magnet (with T_c = 280K) which allows to study chiral excitations directly "on-site" via the ⁵⁷Fe nucleus because of its S=1/2 nuclear spin. NMR provides the local susceptibility (hyperfine field), the dynamic susceptibility (spin lattice relaxation rate SLRR = 1/T₁) and the spin-spin interaction (spin-spin relaxation rate SSRR = 1/T₂). Measurements were performed on crushed single crystals of ⁵⁷Fe enriched FeGe material between 2-300 K in zero and applied magnetic fields. Helical- conical- and field-polarized- states could be clearly identified from NMR and critical dynamics at these transitions are investigated. The field dependence of H_hf, SLRR and SSRR was studied in great detail at various temperatures below T_c. Especially an evidence of the Skyrmion -A- phase formation is given by NMR. Cubic Cu₂OSeO₃ is an oxide with a ferrimagnetic transition at about 60 K. Its magnetic phase diagram - including the Skyrmion phase - is very similar to FeGe. We present first ^63,65Cu NMR results on single crystals at zero field and in modulation fields.