(M=Ni,Fe) compounds*

The perfect triangular lattice is the simplest 2D magnetic lattice to study magnetic frustration which can lead to exotic quantum phenomena. In this work we focus on MGa₂S₄ compounds with a magnetic ion M = Ni, Fe. Both systems crystallize in a perfect layered triangular Fe/Ni-lattice separated by non-magnetic Ga and S atoms. Recent neutron and magnetic susceptibility experiments¹ suggest strong exchange couplings for both systems.

Using ab-initio methods (total-energy mapping analysis and “projED”²) we extract an effective magnetic Hamiltonian including magnetic interactions up to the third next nearest neighbors and single ion anisotropy. We discuss the comparison between neutron scattering intensity of the model for the pristine crystal and experimental results where mixing of the M and Ga cations was suggested.

[1] K. Guratinder et al., Phys. Rev. B 104, 064412 (2021)

[2] K. Riedl et al., Phys. Status Solidi B 256, 1800684 (2019)