Abstract
We use neutron scattering to show that ferromagnetic (FM) phase transition in the two-dimensional (2D) honeycomb lattice CrI3 is a weakly first order transition and controlled by spin-orbit coupling (SOC) induced magnetic anisotropy, instead of magnetic exchange coupling as in a conventional ferromagnet. With increasing temperature, the magnitude of magnetic anisotropy, seen as a spin gap at the Brillouin zone center, decreases in a power law fashion and vanishes at TC, while the in-plane and c-axis spin-wave stiffnesses associated with magnetic exchange couplings remain robust at TC. We also compare parameter regimes where spin waves in CrI3 can be described by a Heisenberg Hamiltonian with Dzyaloshinskii-Moriya interaction or a Heisenberg-Kitaev Hamiltonian. These results suggest that the SOC induced magnetic anisotropy plays a dominant role in stabilizing the FM order in single layer 2D van der Waals ferromagnets.
| Original language | English |
|---|---|
| Article number | 134418 |
| Journal | Physical Review B |
| Volume | 101 |
| Issue number | 13 |
| DOIs | |
| State | Published - Apr 1 2020 |
Funding
We are grateful to R. J. Birgeneau and Andriy Nevidomskyy for helpful discussions. The INS and single crystal synthesis work at Rice was supported by the US NSF Grant No. DMR-1700081 and the Robert A. Welch Foundation Grant No. C-1839 (P.D.), respectively. The work of J.-H.C. was supported by the National Research Foundation of Korea (Grants No. NRF-2016R1D1A1B03934157 and No. NRF2017K1A3A7A09016303). A portion of this research used resources at the Spallation Neutron Source and the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by ORNL. Experiments at the ISIS Neutron and Muon Source were supported by a beam time allocation RB1820251 from the Science and Technology Facilities Council .