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MA: Fachverband Magnetismus

MA 64: Poster 1

MA 64.10: Poster

Freitag, 24. März 2017, 09:30–13:00, P2-EG

Magnetic susceptibility and phase transitions in the B20 helical magnet Mn_1−xCo_xGe — •Patrick Strauss¹, Evgeny Altynbaev², Sven-Arne Siegfried³, Evgeny Moskvin², André Heinemann³, Ludmila Fomicheva⁴, Anatoly Tsvyashchenko⁴, Sergey Grigoriev², and Dirk Menzel¹ — ¹IPKM, TU Braunschweig, Germany — ²PNPI, Gatchina and Saint-Petersburg State University, Russia — ³Helmholtz-Zentrum Geesthacht, Germany — ⁴IHPP, Troitsk, Russia

The non-centrosymmetric transition metal silicides and germanides crystallizing in the cubic B20 structure are well-known for the competing Heisenberg and Dzyaloshinskii-Moriya (DM) interactions leading to incommensurate helical spin structures. The germanides stand out for their relatively high ordering temperatures (278 K for FeGe, e.g.) and complex magnetic phase diagrams. We present a distinct magnetic characterization of the solid solution Mn_1−xCo_xGe measured by SQUID magnetometry. The ordering temperature decreases from T = 200 K for MnGe to T = 25 K for Mn_0.05Co_0.95Ge. Small-angle neutron scattering (SANS) measurements imply that the helical spin structure is driven by RKKY exchange for x < 0.45. In this regime, hysteresis measurements show low anisotropy. In contrast, the exchange is dominated by DM interaction for x > 0.45, which can be supported by an enhanced magnetic anisotropy derived from the magnetization curves. In the high-field regime magnetic transitions are observed which are discussed in the context of the results of the SANS measurements.