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arXiv · 1702.06511

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

N. Martin·M. Deutsch·G. Chaboussant·F. Damay·P. Bonville·L. N. Fomicheva·A. V. Tsvyashchenko·U. K. Rössler·I. Mirebeau
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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.

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N. Martin, M. Deutsch, G. Chaboussant, F. Damay, P. Bonville, L. N. Fomicheva, A. V. Tsvyashchenko, U. K. Rössler, I. Mirebeau. 2017-02-21. 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. https://doi.org/10.1103/physrevb.96.020413

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