  While polar metals are a metallic analogue of ferroelectrics, magnetic polar
metals can be considered as a metallic analogue of multiferroics. There have
been a number of attempts to integrate magnetism into a polar metal by
synthesizing new materials or heterostructures. Here we use a simple yet widely
used approach--epitaxial strain in the search for intrinsic magnetic polar
metals. Via first-principles calculations, we study strain engineering of a
ferromagnetic metallic oxide SrCoO$_3$, whose bulk form crystallizes in a cubic
structure. We find that under an experimentally feasible biaxial strain on the
$ab$ plane, collective Co polar displacements are stabilized in SrCoO$_3$.
Specifically, a compressive strain stabilizes Co polar displacements along the
$c$ axis, while a tensile strain stabilizes Co polar displacements along the
diagonal line in the $ab$ plane. In both cases, we find an intrinsic
ferromagnetic polar metallic state in SrCoO$_3$. In addition, we also find that
a sufficiently large biaxial strain ($> 4\%$) can yield a
ferromagnetic-to-antiferromagnetic transition in SrCoO$_3$. Our work
demonstrates that in addition to yielding emergent multiferroics, epitaxial
strain is also a viable approach to inducing magnetic polar metallic states in
quantum materials.
