Quantum Spin Wave Excited from a Cr-Dy Single-Molecule Magnet

The efficient excitation and controlled propagation of nanoscale spin waves remain significant challenges, as their intrinsic dispersion relations are primarily determined by magnetic dipole and exchange interactions. Here we report the first observed coexistence of quantum spin wave excitation and single-molecule magnet behavior in a mixed chromium(III) and dysprosium(III) complex, namely Dy₄Cr₂(μ₃-F)₂(mdea)₃(piv)₁₀, which shows a large ferrimagnetic ground moment with a restricted quantum tunneling gap (<3.8 × 10^-7 cm^-1) up to nine levels, leading to an axial anisotropic energy barrier of 12 cm^-1 and opened hysteresis loop at 0.4 K. More importantly, quantized spin wave excitations ranging from 108 to 352 GHz have been observed by using inelastic neutron scattering spectroscopy, and the data can be well explained by the L&E-band theory with Δ/2 = 2.08 cm^-1 and ϵ(q) = 2.5 cm^-1, providing unambiguous evidence for nanoscale spin waves.