Partial ordering and phase elasticity in the MnGe short-period helimagnet

N. Martin (1) , I. Mirebeau (1) , C. Franz (2) , G. Chaboussant (3) , L. Fomicheva (4) , N. Fomicheva (4) , A. Tsvyashchenko (4)

1 LLB - UMR 12 - Laboratoire Léon Brillouin
2 TUM - Technische Universität Munchen - Université Technique de Munich [Munich, Allemagne]
3 GIM - Groupe Interfaces et matériaux
4 Vereshchagin Institute for High Pressure Physics

We study the helimagnetic ground state of the MnGe cubic alloy using small-angle neutron scattering and a high-resolution method, the so-called MIEZE spectroscopy. Upon cooling below the Néel temperature $T_N$ = 170(5) K, we observe the proliferation of long-wavelength $gapless$ spin fluctuations, concomitant with a continuous evolution of the helical correlation length. These fluctuations disappear at $T_{com}$ = 32(5) K when the helical period becomes commensurate with the lattice. We propose to describe this intermediate phase as a soliton lattice, promoting nonlinear collective modes, or $phasons$, over a large temperature interval. We discuss the possible relevance of our results to the previously observed magnetotransport anomalies.

Domains: Physics [physics]; Physics [physics]; Condensed Matter [cond-mat]

N. Martin, I. Mirebeau, C. Franz, G. Chaboussant, L. Fomicheva, et al.. Partial ordering and phase elasticity in the MnGe short-period helimagnet. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2019, 99, pp.100402. ⟨10.1103/PhysRevB.99.100402⟩. ⟨cea-02074769⟩