Speaker
Mr.
Jose Lado
(International Iberian Nanotechnology Laboratory)
Description
The observation of ferromagnetic order in a monolayer of CrI 3 has been recently reported,
with a Curie temperature of 45 Kelvin 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, both favoring off-plane magnetization and
contributing to open 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 easy
axis 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.
Primary author
Mr.
Jose Lado
(International Iberian Nanotechnology Laboratory)
Co-author
Joaquin Fernandez-Rossier
(International Iberian Nanotechnology Laboratory)
