Adsorption of monolayer penta-CdSe2 by 3d transition-metal atoms and their dimers: A first-principles study

Materials with high magnetic anisotropy are widely used in magnetic storage. In this work, we systematically investigated the structural stability, electronic structure and magnetic properties of the CdSe${}_2$ monolayer adsorbed by Cr, Mn, Fe and Co atoms and their dimers by first-principles calculations. It is shown that the most stable adsorption sites are located at the positions of bridge bonds formed by Se–Se atoms, the adsorption of atoms and dimers on the CdSe${}_2$ monolayer is chemisorbed. All adsorption systems are magnetic semiconductors, and the system adsorbed Ir–Co dimer is a magnetic metal. The total magnetic moments of the systems adsorbed by the Cr, Mn, Ir and Co atoms are 4.00 ${\mu }_B$, 5.00 ${\mu }_B$, 4.00 ${\mu }_B$ and 3.00 ${\mu }_B$, respectively, the mechanisms of forming integer total magnetic moments and magnetic semiconductor band gaps are discussed by the hybridization, occupation and distribution of electronic states in the crystal field. The CdSe${}_2$ adsorbed by Ir–Cr, Ir–Mn, Ir–Fe and Ir–Co dimers exhibit large magnetic anisotropy energies (MAEs) of 27.15 meV, -49.29 meV, 29.24 meV and 27.90 meV, respectively, and the origin of the MAEs is explained by the second-order perturbation theory of magnetic anisotropy. In addition, the largest MAE of the adsorbed systems reaches 33.28 meV by applying -4%$\sim$4% biaxial strain. In conclusion, our research provides a valuable exploration for the design of materials with larger magnetic anisotropy by the 2D materials adsorbed by atoms or dimers.