Regensburg 2013 – scientific programme

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MA: Fachverband Magnetismus

MA 45: Magnetic Coupling and Spin Structures

MA 45.7: Talk

Thursday, March 14, 2013, 16:45–17:00, H10

⁵⁷Fe NMR as a local probe for chiral ferromagnetism in non-centrosymmetric FeGe — •Michael Baenitz¹, Panchanan Khuntia¹, Markus Schmidt¹, Ulrich Roessler², and Heribert Wilhelm³ — ¹Max-Planck-Institute for the Chemical Physics ofSolids, 01187 Dresden, Germany — ²Leibniz Institutefor Solid State and Materials Research - IFW, 01171 Dresden, Germany — ³Diamond Light Source Ltd, Didcot, OxfordshireOX11 0DE, United Kingdom

The helical ferromagnet FeGe belongs to the class of B20 compounds with non-centrosymmetric structure being essential for new forms of ferromagnetic phases (confined or modulated Skyrmion phase). From an NMR point FeGe is a prototype system to study chiral excitations directly "on-site" via the ⁵⁷Fe nucleus which (in contrast to ⁵⁵Mn with nuclear spin S=5/2) has a spin of S=1/2 with the big advantage of an absent quadrupolar interaction which usually creates broad NMR lines and prevents detailed investigations of the anisotropic Zeeman interaction in internal/external fields. ⁵⁷Fe NMR opens up to probe the local susceptibility (hyperfine field), the dynamic susceptibility (spin lattice relaxation rate) and the spin-spin interaction directly "on site". Additionally the NMR line itself (its Fourier transform) provides information about the multiplicity of the Fe sites in the complex helimagnet. ⁵⁷Fe NMR was performed on crushed single crystals of ⁵⁷Fe enriched FeGe material between 2-300 K in zero and applied magnetic fields. Phase boundaries in the ordered state are identified and interestingly critical dynamics in the vicinity of these boundaries are obtained from the spin-lattice and spin-spin relaxation rate.