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MA: Fachverband Magnetismus
MA 9: Magnetic Materials I
MA 9.7: Vortrag
Montag, 14. März 2011, 16:15–16:30, HSZ 401
Precursor Phenomena at the Magnetic Ordering of the cubic Helimagnet FeGe — •Michael Baenitz1, Heribert Wilhelm2, Marcus Schmidt1, Ulrich K. Rößler3, Alexei N. Bogdanov3, and Andrey A. Leonov3 — 1MPI CPfS, Noethnitzer Str. 40, 01187 Dresden — 2Diamond Light Source Ltd., Chilton, Didcot, OX11 0DE, United Kingdom — 3IFW Dresden, Postfach 270116, 01171 Dresden
We report on detailed magnetic measurements on the cubic helimagnet FeGe in external magnetic fields parallel to the [100] direction and temperatures in the vicinity of the onset of long-range magnetic order at Tc≈ 278 K. Depending on the temperature and field, a helical state (H<Hc1), a conical phase (Hc1<H<Hc2), or the so-called A-phase were observed below Hc2 at which the field-polarized state occurs. Precursor phenomena found above Tc display a complex succession of temperature-driven cross-overs and phase transitions. The A-phase pocket is split in at least two distinct areas, A1 and A2. The area A1 at lower fields shows clear lines of transitions into the conical phase at lower temperature and into the A2 area at higher fields. The area A2 appears to transform continuously into the conical phase. Relying on a modified phenomenology for chiral magnets, the A1 phase could indicate existence of a +π Skyrmion lattice, however, the A2 phase seems related to helicoids propagating in directions perpendicular to the applied field. We suggest that the observation of this A2-phase can be explained by hexagonal arrays of spiral domains consisting essentially of helicoids.