  The effect of strain on the magnetic order and band structure of single-layer
CrAsS$_4$ has been investigated by first-principles calculations based on
density functional theory. We found that single-layer CrAsS$_4$ was an
antiferromagnetic (AFM) semiconductor, and would have a phase transition from
AFM state to ferromagnetic (FM) state by applying a uniaxial tensile strain of
2.99\% along the y-direction or compressive strain of 1.76\% along the
x-direction. The underlying physical mechanism of strain-dependent magnetic
stability was further elucidated as the result of the competition between the
direct exchange and indirect superexchange interactions. Moreover, band gap
exhibit a abrupt change along with phase transition of magnetic order. Our
study provides an intuitional approach to design strain-modulated spintronic
devices.
