Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 60: Spin Structures and Magnetic Phase Transitions

MA 60.3: Vortrag

Donnerstag, 17. März 2011, 18:00–18:15, HSZ 103

(contribution withdrawn, duplicate of TT 4.3) Spin echo measurements of magnetic fluctuations in helical Mn_1−xFe_xSi — •Alexander Tischendorf¹, Wolfgang Häußler^1,2, Andreas Bauer¹, Peter Böni¹, and Christian Pfleiderer¹ — ¹Technische Universität München, Physik Department E21, 85748 Garching, Germany — ²Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), 85748 Garching, Germany

Manganese silicide (MnSi) is a 3d inter metallic compound and crystallizes in a cubic B20 structure. In absence of an external magnetic field for temperatures below T_c the magnetization caused by the spin of the electrons forms a chiral long-period ferromagnetic helix with a period of approximately 180 Å. Furthermore, the phase transition temperature in Mn_1−xFe_xSi changes with the conzentration x. At a critical concentration x_c the phase transition temperature T_c=0 and there is a quantum phase transition (QPT).

By means of neutron spin echo we investiaged the linewidth of magnetic fluctuations in absence of an external magnetic field. The high energy resolution and the small angle scattering set up of the spin echo instrument RESEDA at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) offer paramter ranges, which are not accessable in triple axes measurements. We measured the linewidth in dependence of different temperatures and Q-values in pure MnSi and also compared them to an iron doped sample. The measured linewidth will be discussed, regarding the spin-fluctuation theory of weakly magnetic itinerant-electron compounds, which allows the identification of anomalous behavior at QPTs.