Two-dimensional (2D) antiferromagnetic manganese chalcogenides
have been successfully synthesized recently. However, the electronic
and magnetic properties of these new materials have not been clearly
understood. The absence of net magnetization and a large electronic
band gap may hinder their application. In this work, we systematically
studied the electronic and magnetic properties of the semihydrogenated
MnX (donated as H@MnX, X = S, Se, Te) monolayers. The hydrogen atoms
can stably adsorb onto the Mn ions. In the hydrogenated Mn sublayer,
the magnetic couplings between adjacent Mn ions become ferromagnetic,
while the magnetic couplings in the other Mn sublayer and the intersublayer
magnetic couplings remain antiferromagnetic. Consequently, the magnetic
ground state becomes ferrimagnetic, with a net magnetic moment of
0.5 μB per Mn. The critical temperatures of the ferrimagnetic
order for H@MnSe and H@MnTe are ∼180 and ∼200 K, respectively.
Semihydrogenation also greatly changes the electronic structures of
MnX. The electronic band gaps of MnX monolayers are reduced from 3.87,
3.41, and 3.09 eV to 1.21, 0.66, and 0.25 eV, respectively. Particularly,
H@MnTe exhibits a direct band gap. A biaxial in-plane strain can further
tune the magnetic behaviors of the H@MnX monolayers. These findings
provide a practical route to manipulating the electronic and magnetic
properties of 2D magnetic semiconductors for advanced spintronic applications.