Dynamic spin correlations in the frustrated cubic phase of MnV ₂O₄

The ferrimagnetic spinel MnV₂O₄ undergoes an orbital-induced cubic-to-tetragonal distortion at T_YK=58 K, below which noncollinear commensurate ferrimagnetic ordering occurs. Using inelastic neutron scattering, we investigated low-energy dynamics in its cubic phase above T_YK. We observed two types of coexisting short-range magnetic excitations: the dispersive spin waves centered around the Brillouin-zone centers, k₀ = (0, 0, 0), and quasielastic spin fluctuations centered at incommensurate wave vectors, k_incom = (ξ, ξ, 0). The coexistence of the two distinct features can be understood as a dynamic realization of the conical spiral order observed in cubic spinels such as CoCr₂O₄.