Hydrogen-induced ferromagnetism in two-dimensional Pt dichalcogenides

Electronic, structural, and magnetic properties of Pt dichalcogenide monolayers are investigated using first-principle calculations. We find that hydrogenation lifts the spin degeneracy in narrow antibonding Pt $5d$ subband electrons and transforms the nonmagnetic semiconductors $\mathrm{Pt}{X}_2(X=\mathrm{S},\mathrm{Se},\mathrm{Te})$ into ferromagnetic metals, $\mathrm{Pt}{X}_2$-1H; neither strain nor thin-film edges are necessary to support the transition. The trend towards ferromagnetism is most pronounced for $X=\mathrm{S}$, decreasing with increasing atomic weight of the chalcogens.

Figure 1

Atomic structure of monolayers of 1T $\mathrm{Pt}{X}_2(X=\mathrm{S},\mathrm{Se},\mathrm{Te})$: (a) top view and (b) side view.

Figure 2

Calculated band structures of the monolayers: (a) $\mathrm{Pt}{\mathrm{S}}_2$, (b) $\mathrm{PtS}{\mathrm{e}}_2$, and (c) $\mathrm{PtT}{\mathrm{e}}_2$. The dashed line indicates the Fermi level.

Figure 3

Different spin configurations in $\mathrm{Pt}{\mathrm{H}}_2\text{−}1\mathrm{H}$: (a) ferromagnetic and (b)–(d) antiferromagnetic. For simplicity, all calculations have been performed for a $4\times 4\times 1$ supercell.

Figure 4

Spin-density distribution: Top view on a spin-density isosurface of a ferromagnetic monolayer of $\mathrm{Pt}{\mathrm{S}}_2\text{−}1\mathrm{H}$.

Figure 5

Calculated monolayer band structures along high-symmetry directions: (a) $\mathrm{Pt}{\mathrm{S}}_2\text{−}1\mathrm{H}$, (b) $\mathrm{PtS}{\mathrm{e}}_2\text{−}1\mathrm{H}$, and (c) $\mathrm{PtT}{\mathrm{e}}_2\text{−}1\mathrm{H}$. The orange and blue lines represent spin-up and spin-down bands, respectively.

Figure 6

Calculated spin-polarized partial density of states: (a)–(c) $\mathrm{Pt}{\mathrm{S}}_2\text{−}1\mathrm{H}$, (d)–(f) $\mathrm{PtS}{\mathrm{e}}_2\text{−}1\mathrm{H}$, and (g)–(i) $\mathrm{PtT}{\mathrm{e}}_2\text{−}1\mathrm{H}$.