  In this paper, spin properties of monolayer MX (M=Ga, In and X=S, Se, Te) in
the presence of strain are studied. Density functional theory is used to
investigate spin properties. The strain changes modification of bandgap due to
spin-orbit coupling, the results indicate the spin-orbit coupling has a higher
effect in the compressive regime. Also, spin splitting in the conduction and
valence bands respect to strain are compared for six materials. The location of
conduction band minimum (CBM) imposed a type of spin properties. These
materials with mirror symmetry can display the Rashba effect while M valley is
located at CBM. Strain tunes the conduction band minimum in three valleys (K, M
and $\Gamma$ valleys) and determines which spin effect (spin splitting, Rashba
splitting or no spin splitting) has occurred in each strain for every material.
Lastly, the relation between the Rashba parameter and the atomic mass is
explored and it is observed that there is a linear correlation between atomic
mass and Rashba coefficient.
