  We analyze the effects of chemical pressure induced by alkali metal
substitution and uniaxial strain on magnetism in the A2Cr3As3 (A = Na, K, Rb,
Cs) family of ternary arsenides with quasi-one dimensional structure. Within
the framework of the density functional theory, we predict that the
non-magnetic phase is very close to a 3D collinear ferrimagnetic state, which
realizes in the regime of moderate correlations, such tendency being common to
all the members of the family with very small variations due to the different
interchain ferromagnetic coupling. We uncover that the stability of such
interchain ferromagnetic coupling has a non-monotonic behavior with increasing
the cation size, being critically related to the degree of structural
distortions which is parametrized by the Cr-As-Cr bonding angles along the
chain direction. In particular, we demonstrate that it is boosted in the case
of the Rb, in agreement with recent experiments. We also show that uniaxial
strain is a viable tool to tune the non-magnetic phase towards an interchain
ferromagnetic instability. The modifcation of the shape of the Cr triangles
within the unit cell favors the formation of a net magnetization within the
chain and of a ferromagnetic coupling among the chains. This study can provide
relevant insights about the interplay between superconductivity and magnetism
in this class of materials.
