  Recently the discovery of magnetic order in two-dimensional monolayer
chromium trihalides opens the new research field in two-dimensional materials.
We use first-principles calculations to systematically examine the doping
effect of chalcogen on CrBr3. In the case of S-doping, four stable
configurations, Cr2Br5S, Cr2Br4S2-A, Cr2Br4S2-B and Cr2Br3S3-A, are predicted
to be ferromagnetic semiconductors. It is found that the new bands appearing in
the original bandgap are made up of S-p and Cr-d-egorbits, lead to the obvious
reduce of bandgap and the enhanced optical absorption in the visible range. Due
to the decrease of valence electron after chalcogen doping, the magnetic moment
also decreases with the increase of S atoms, and the character of ferromagnetic
semiconductor is always hold in a wide range of strain. The results shown that
monolayer CrBr3with chalcogen doping supply a effectual way to control the
magnetism and extend the optoelectronic applications.
