Role of exchange splitting and ligand field splitting in tuning the magnetic anisotropy of an individual iridium atom on TaS2 substrate

In this work, using first-principle calculation we investigate the magnetic anisotropy (MA) of single-atom iridium (Ir) on TaS2 substrate. We find that the strength and direction of MA in the Ir adatom can be tuned by strain. The MA arises from two sources, namely spin-conservation term and spin-flip term. The spin-conservation term is generated by spin-orbit coupling (SOC) interaction on dxy/dx2-y2 orbitals and is contributed to the out-of-plane MA. The spin-flip term is caused by SOC interaction on dxz/dyz and px/py orbitals and is responsible for the in-plane MA. We further find that strain-tuned MA is mainly determined by exchange splitting and ligand field splitting. Increase of strain will enhance the exchange splitting and reduce the ligand field splitting, resulting in the enhancement of the in-plane MA from dxy/dx2-y2 orbitals and the reduction of the out-of-plane MA from dxz/dyz and px/py orbitals, and hence leading to the change of the strength and direction of the total MA. Our study provides a way for tuning the MA of single-atoms magnet on 2D transition metal dichalcogenides substrate by control of the exchange splitting and the ligand field splitting.