Hydrogen functionalization induced two-dimensional ferromagnetic semiconductor in Mn di-halide systems

We explored the electronic and magnetic properties of two-dimensional manganese di-halides (MnY2, Y = I, Br, Cl) and hydrogenated systems (MnHY2). The pristine MnY2 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 mu(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 MnY2 structure was broken and the FM ground state was obtained in all MnHY2 systems. We obtained a negative spin polarization in the H atom and the magnetic moment of the Mn atom decreased from 5 mu(B) to 4 mu(B). However, this negative polarization played a pivotal role in inducing a FM ground state in the MnHY2 systems. Furthermore, the asymmetric spin dependent bang gap in MnHY2 was also greatly enhanced due to this hydrogenation as compared with that in the pristine MnY2 systems. This finding suggests that the hydrogenated MnHY2 can be used as a potential ferromagnetic semiconductor for spintronics.