Modulation of electronic and magnetic properties of monolayer chromium trihalides by alloy and strain engineering

Monolayer CrI3 is a rare ferromagnetic semiconductor with intrinsic long-range magnetic order, which makes it a great potential material in spintronic devices [Song et al., Science 360, 1214 (2018)]. To extend the applications of monolayer CrI3 in flexible devices, the modulation of its electronic and magnetic properties is important. Here, we investigated the combined effect of strain and alloy on the properties of monolayer CrI3 by first-principles calculations. Br is chosen as the alloyed element due to the similar atomic configuration and property of CrX3 (X=Br, I), and the strain is applied by simultaneously changing the in-plane lattice constants (a and b). We find that the bandgap of monolayer Cr2I6-xBrx can be tuned greatly, while the magnetic moment of monolayer Cr2I6-xBrx is regulated very little under different strain and Br concentration. This unique property of monolayer Cr2I6-xBrx under strain makes it a good candidate for the flexible spintronic devices.