Long period helical structures and twist-grain boundary phases induced by non magnetic ion doping in Mn${}_{1-x}$(Co,Rh)${}_x$Ge chiral magnet

Abstract

We study the evolution of helical magnetism in MnGe chiral magnet upon partial substitution of Mn for non magnetic 3d-Co and 4d-Rh ions. At high doping levels, we observe spin helices with very long periods -more than ten times larger than in the pure compound- and sizable ordered moments. This behavior calls for a change in the energy balance of interactions leading to the stabilization of the observed magnetic structures. Strikingly, neutron scattering unambiguously shows a double periodicity in the observed spectra at $x\gtrsim 0.45$ and $\gtrsim 0.25$ for Co- and Rh-doping, respectively. In analogy with observations made in cholesteric liquid crystals, we suggest that it reveals the presence of magnetic twist-grain-boundary phases, involving a dense short-range correlated network of screw dislocations. The dislocation cores are described as smooth textures made of non-radial double-core skyrmions.

arXiv comment6 pages, 6 figures

References in corpus (11)

• Skyrmions with varying size and helicity in composition-spread helimagnetic alloys
• Three-dimensional skyrmion states in thin films of cubic helimagnets
• Smectic Liquid Crystals in Random Environments
• Doppler shift picture of the Dzyaloshinskii--Moriya interaction
• Dzyaloshinskii-Moriya interaction and Hall effects in the skyrmion phase of MnFeGe alloys
• Three-dimensional chiral skyrmions with attractive interparticle interactions
• Why stripes? Spontaneous formation of inhomogeneous structures due to elastic interactions
• Nonlinear smectic elasticity of a helical state in cholesterics and helimagnets
• Magnetic ground state and spin fluctuations in MnGe chiral magnet as studied by Muon Spin Rotation
• Multi-shell contribution to the Dzyaloshinskii-Moriya spiralling in MnSi-type crystals
• Magnetovolume effect, macroscopic hysteresis and moment collapse in the paramagnetic state of cubic MnGe under pressure

Cited by in corpus (8)

• Screw dislocations in cubic chiral magnets
• Exploring the origins of the Dzyalloshinski-Moria interaction in MnSi
• Complex magnetism of B20-MnGe: from spin-spirals, hedgehogs to monopoles
• Magnetic, electronic and transport properties of high-pressure-synthesized chiralmagnets Mn${}_{1-x}$Rh${}_x$Ge (B20)
• Fragile balance of the exchange interactions in Mn${}_{1-x}$Co${}_x$Ge compounds
• Theoretical and experimental study of high-pressure synthesized B20-type compounds Mn${}_{1-x}$(Co,Rh)${}_x$Ge
• Cubic B20 helimagnets with quenched disorder in magnetic field
• Effect of interfacial Dzyaloshinskii-Moriya interaction on polarized neutrons reflection