Intrinsic instability of the helix spin structure in MnGe and order-disorder phase transition.

E. Altynbaev, S.-A. Siegfried, V. Dyadkin, E. Moskvin, D. Menzel, A. Heinemann, C. Dewhurst, L. Fomicheva, A. Tsvyashchenko, S. Grigoriev

Research output

17 Citations (Scopus)

Abstract

The magnetic structure of the cubic helimagnet MnGe was studied by small-angle neutron scattering in a wide temperature range from 10 to 300 K. We show that MnGe undergoes a complex order-disorder phase transition covering more than 100 K above the critical temperature TN=(130±2) K. Moreover, the helical structure is intrinsically unstable below TN, since the profile of the reflection at kh∼2 nm−1 associated with the spin helix can be described by the sum of Gaussian and Lorentzian contributions, indicating a stable helix and spin-helix fluctuations, respectively. The Gaussian behavior determines the system at low temperature, whereas the Lorentzian is negligible. With increasing temperature, however, the Lorentzian starts to contribute and dominates at TN. The spin-helix fluctuations are accompanied by intensive spin excitations observed in small-angle neutron scattering as Q-independent scattering at Q
Original languageEnglish
Pages (from-to)174420_1-6
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume90
Issue number17
DOIs
Publication statusPublished - 2014

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