Observation of the Griffiths phase in the hyperkagome antiferromagnet Mn3RhSi in the absence of disorder

Abstract The disorder has been believed to be a necessary ingredient in the Griffiths phase, which usually forms a ferromagnetic cluster in the paramagnetic state above the magnetic long-range order temperature. However, we found that the Griffiths phase behavior appears as a magnetic short-range order in a paramagnetic state of a hyperkagome antiferromagnet Mn3RhSi without any disorder over a wide temperature range of approximately 500 K. Here, neutron scattering investigations of the magnetic Griffiths phase in a single crystal of Mn3RhSi reveal the fluctuating magnetic cluster forms a spiral spin structure different from the Néel state. This finding suggests that the magnetic Griffiths phase becomes stable in the paramagnetic state of the hyperkagome lattice without any disorders.