  Antiferromagnets have no net spin-splitting on the scale of the
superconducting coherence length. Despite this, antiferromagnets have been
observed to suppress superconductivity in a similar way as ferromagnets, a
phenomenon that still lacks a clear understanding. We find that this effect can
be explained by the role of impurities in antiferromagnets. Using
quasiclassical Green's functions, we study the proximity effect and critical
temperature in diffusive superconductor-metallic antiferromagnet bilayers. The
non-magnetic impurities acquire an effective magnetic component in the
antiferromagnet. This not only reduces the critical temperature but also
separates the superconducting correlations into short-ranged and long-ranged
components, similar to ferromagnetic proximity systems.
