  Conventional superconductors disordered by magnetic impurities demonstrate
physical properties drastically different from their pristine counterparts. In
our previous work [Phys. Rev. B 92, 245430 (2015)] we explored spectral and
thermodynamic properties of such systems for two extreme cases: completely
random and ferromagnetically aligned impurity magnetic moments. Here we
consider transport properties of these systems, and show that they have a
potential to be used in superconducting spintronic devices. Each magnetic
impurity contributes a Yu-Shiba-Rusinov (YSR) bound state to the spectrum,
residing at sub-gap energies. Provided the YSR states form metallic bands, we
demonstrate that the tunneling current carried by these states can be highly
spin-polarized when the impurities are ferromagnetically ordered. The spin
polarization can be switched by simply tuning the bias voltage. Moreover, even
when the impurity spins are completely uncorrelated, one can still achieve
almost 100% spin polarization of the current, if the tunnel interface is
spin-active. We compute electric current and noise, varying parameters of the
interface between tunneling and fully transparent regimes, and analyze the
relative role of single-particle and Andreev reflection processes.
