Two-dimensional ferromagnetic spin-orbital excitations in honeycomb VI3

VI3 is a ferromagnet with planar honeycomb sheets of bonded V3+ ions held together by van der Waals forces. We apply neutron spectroscopy to measure the two-dimensional (J/J(c) approximate to 17) magnetic excitations in the ferromagnetic phase, finding two energetically gapped (Delta approximate to k(B)T(c) approximate to 55 K) and dispersive excitations. We apply a multilevel spin-wave formalism to describe the spectra in terms of two coexisting domains hosting differing V3+ orbital ground states built from contrasting distorted octahedral environments. This analysis fits a common nearest-neighbor in-plane exchange coupling (J = -8.6 +/- 0.3 meV) between V3+ sites. The distorted local crystalline electric field combined with spin-orbit coupling provides the needed magnetic anisotropy for spatially long-ranged two-dimensional ferromagnetism in VI3.

Automated summary

VI3 is a ferromagnet with planar honeycomb sheets of bonded V3+ ions held together by van der Waals forces. Neutron spectroscopy is applied to measure two-dimensional magnetic excitations in the ferromagnetic phase. The study reveals the mechanism of magnetic anisotropy in VI3, providing insights into its spatially long-ranged two-dimensional ferromagnetism.