Strain engineering the magnetic states of vacancy-doped monolayer MoSe2

• The effects of vacancy defects and biaxial strain on the magnetic property of MoSe2 were investigated.
• VSe, VSe2 and VMoSe3 vacancy doped MoSe2 monolayer are nonmagnetic, while VMoSe6 vacancy geometry shows magnetic moment.
• The combined vacancy doping and tensile strain can effectively tune the magnetism in MoSe2 monolayer.

The effect of vacancy defect and strain on the magnetic property of monolayer MoSe2 was investigated by the first-principles calculation. Firstly, the most stable structure of monolayer MoSe2 and four kinds of vacancy, VSe, VSe2, VMoSe3 and VMoSe6 geometries were systematically studied. Our calculations show that 1H-MoSe2, as well as VSe, VSe2 and VMoSe3 vacancy doped MoSe2 monolayer are nonmagnetic, while VMoSe6 vacancy geometry shows magnetism and the magnetic moment mainly comes from the six Mo atoms around the vacancy although it is most difficult to form. Meanwhile, our calculations indicate that MoSe2 monolayer under tensile strain ranging from 0% to 10% does not show any magnetism. However, it is found that the combined tensile strain and VSe, or VSe2 and VMoSe3 vacancy indeed induce magnetism in MoSe2 monolayer by breaking the Mo–Mo metallic bonds. As for VMoSe6 vacancy geometry, the vacancy induced magnetic moment decrease under the imposed tensile strain.