2020 年 30 巻 3 号 p. 144-148
We report topological magnetic phase transitions between skyrmion lattice state and hedgehog lattice state realized in cubic chiral magnets MnSi1-xGex. By performing small- and wide-angle neutron scattering experiments, we discover three different topological spin textures with variation of the lattice constant controlled by Si/Ge substitution: skyrmion lattice (x = 0-0.25) and two types of hedgehog lattices with four q-vectors (x = 0.4-0.6) and three q-vectors (x = 0.7-1.0). The variation of magnetic properties in MnSi1-xGex strongly suggests that short-period hedgehog lattices may be stabilized by conduction electron mediated exchange interactions, rather than Dzyaloshinskii-Moriya interaction. We also discuss some recent theoretical proposals concerning the stabilization mechanism of the hedgehog lattices, which are related to high-order exchange interactions.
