期刊
2D MATERIALS
卷 4, 期 3, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/2053-1583/aa75ed
关键词
magnetism; spin wave; magnetic anisotropy; chromium iodine
资金
- Marie-Curie-ITN [607904-SPINOGRAPH]
- MEC-Spain [MAT2016-78625-C2]
- ERDF funds through the Portuguese Operational Program for Competitiveness and Internationalization COMPETE 2020
- National Funds through FCT-The Portuguese Foundation for Science and Technology [PTDC/FIS-NAN/4662/2014 (016656)]
The observation of ferromagnetic order in a monolayer of CrI3 has been recently reported, with a Curie temperature of 45 K and off-plane easy axis. Here we study the origin of magnetic anisotropy, a necessary ingredient to have magnetic order in two dimensions, combining two levels of modeling, density functional calculations and spin model Hamiltonians. We find two different contributions to the magnetic anisotropy of the material, favoring off-plane magnetization and opening a gap in the spin wave spectrum. First, ferromagnetic super-exchange across the. 90 degree Cr-I-Cr bonds, are anisotropic, due to the spin-orbit interaction of the ligand I atoms. Second, a much smaller contribution that comes from the single ion anisotropy of the S = 3/2 Cr atom. Our results permit to establish the XXZ Hamiltonian, with a very small single ion anisotropy, as the adequate spin model for this system. Using spin wave theory we estimate the Curie temperature and we highlight the essential role played by the gap that magnetic anisotropy induces on the magnon spectrum.
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