Magnetic ground states and spin dynamics of β-Mn1-xRux alloys

The geometrical frustration of the β-Mn lattice suppresses moment formation, leading to a spin-liquid ground state. Alloying β-Mn to expand the unit cell results in moment localization, but the resulting ground state is normally a spin glass. However, alloys of β-Mn with Ru and Os were found to exhibit long-range order. This paper reports a study of the low-frequency spin dynamics in β-MnRu alloys using muon spin relaxation, supported by susceptibility, heat capacity and neutron diffraction data. For Ru concentrations ≤9 at.%, spin-glass ground states are found. Antiferromagnetism is found at higher concentrations, but at low temperatures there is evidence for a coexistent spin-glass state