Two-step pressure-induced collapse of magnetic order in the MnGe chiral magnet

Cubic helimagnets such as MnSi and FeGe have provided paradigmatic cases of pressure-induced collapse of band ferromagnetism in metals, accompanied with exotic partial order and chiral spin textures. Isostructural MnGe stands out owing to its much shorter helix pitch and high magnetic moment. By combining resistivity, ac susceptibility, and neutron diffraction measurements under very high pressure, we show that the helical order in MnGe transforms around 6 GPa from a high- spin to a low-spin state, recalling the weak ferromagnetism of MnSi at ambient pressure. Helical order collapses only above 10 GPa. The spin-state transition is supported by ab initio calculations.