Abstract
We explored the electronic and magnetic properties of two-dimensional manganese di-halides (MnY
2
, Y = I, Br, Cl) and hydrogenated systems (MnHY
2
). The pristine MnY
2
monolayers had a very weak magnetic exchange interaction and we found degenerated magnetic states between ferromagnetic and antiferromagnetic states although the Mn had a high magnetic moment of 5
μ
B
with a finite band gap. However, we found that the electronic band structure and magnetic properties could be significantly altered by functionalization with hydrogen atoms because the degeneracy in the pristine MnY
2
structure was broken and the FM ground state was obtained in all MnHY
2
systems. We obtained a negative spin polarization in the H atom and the magnetic moment of the Mn atom decreased from 5
μ
B
to 4
μ
B
. However, this negative polarization played a pivotal role in inducing a FM ground state in the MnHY
2
systems. Furthermore, the asymmetric spin dependent bang gap in MnHY
2
was also greatly enhanced due to this hydrogenation as compared with that in the pristine MnY
2
systems. This finding suggests that the hydrogenated MnHY
2
can be used as a potential ferromagnetic semiconductor for spintronics.