Topological magnetic structures in MnGe: Neutron diffraction and symmetry analysis

Abstract

From new neutron powder diffraction experiments on the chiral cubic ($P2{}_{1}3$) magnet manganese germanide MnGe, we analyse all of the possible crystal symmetry-allowed magnetic superstructures that are determined successfully from the data. The incommensurate propagation vectors $k$ of the magnetic structure are found to be aligned with the [100] cubic axes, and correspond to a magnetic periodicity of about 30 $\mathring{A}$ at 1.8 K. Several maximal crystallographic symmetry magnetic structures are found to fit the data equally well and are presented. These include topologically non-trivial magnetic hedgehog and "skyrmion'' structures in multi-$k$ cubic or orthorhombic 3+3 and orthorhombic 3+2 dimensional magnetic superspace groups respectively, with either potentially responsible for topological Hall effect. The presence of orthorhombic distortions in the space group $P{2}_1{2}_1{2}_1$ caused by the transition to the magnetically ordered state does not favour the cubic magnetic hedgehog structure, and leave both orthorhombic hedgehog and "skyrmion'' models as equal candidates for the magnetic structures. We also report on a new combined mechanochemical and solid-state chemical route to synthesise MnGe at ambient pressures and moderate temperatures, and compare with samples obtained by the traditional high pressure synthesis.

arXiv commentNew high-resolution neutron diffraction data are added that allows us to unambiguously determine a preference for the orthorhombic symmetry

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Cited by in corpus (5)

• Hidden Topological Transitions in Emergent Magnetic Monopole Lattices
• Theory of collective excitations in the quadruple-$Q$ magnetic hedgehog lattices
• Observation of magnetic skyrmion lattice in Cr${}_{0.82}$Mn${}_{0.18}$Ge by small-angle neutron scattering
• On the magnetic contribution of itinerant electrons to neutron diffraction in the topological antiferromagnet CeAlGe
• Structure and magnetism of MnGe thin films grown with a nonmagnetic CrSi template