Tunable electronic and magnetic properties of monolayer and bilayer Janus Cr2Cl3I3: a first-principles study

Recently, novel two-dimensional (2D) magnetic materials have drawn enormous research attention due to their interesting tunable electronic and magnetic properties. However, 2D Janus materials with intrinsic magnetism are rare. We investigate the geometric and electronic properties of monolayer (ML) and bilayer (BL) intrinsic magnetic Janus Cr2Cl3I3 using first-principles calculations. We find that ML Janus Cr2Cl3I3 is a magnetic semiconductor with the band gaps for the spin-alpha and spin-beta channels being 2.11 and 3.83 eV, respectively. The magnetic ground state of ML Cr2Cl3I3 can be effectively modulated by biaxial strain from the ferromagnetic (FM) state to the antiferromagnetic (AFM) state. Meanwhile, ML Cr2Cl3I3 experiences an electronic phase transition from a half semiconductor (HSC) to a bipolar magnetic semiconducor (BMS) and finally a spin-unpolarized semiconductor with increasing strain. More interestingly, as the biaxial strain increases, the Curie temperature for the FM ground state increases from 36.3 K to 49.2 K. As for bilayer (BL) Cr2Cl3I3, the stacking order could effectively affect the magnetic and electronic properties. The most stable stacking order is AB-II type, followed by AA-II, AB-ClI, AA-ClI, AB-ClCl and AA-ClCl stacking orders. They are all spin-polarized BMS. The magnetic and electronic properties of BL Cr2Cl3I3 change with different stacking orders, possibly due to the quantum confinement effect and interlayer interactions. The stability of ML Cr2Cl3I3 is confirmed by the phonon spectrum and molecular dynamics simulations. The tunable electronic properties together with intrinsic ferromagnetism enrich the diversity of Janus 2D Cr2Cl3I3, which has potential applications in spintronic devices.