  Correlation effects play an important role in the electronic structure of
half-metallic (HM) magnets. In particular, they give rise to non-quasiparticle
states above (or below) the Fermi energy at finite temperatures that reduce the
spin polarization and, as a consequence, the efficiency of spintronics devices.
Employing the constrained random-phase approximation (cRPA) within the
full-potential linearized augmented-plane-wave (FLAPW) method using maximally
localized Wannier functions, we calculate the strength of the effective on-site
Coulomb interaction (Hubbard $U$ and Hund exchange $J$) between localized
electrons in different classes of HM magnets considering: (i)
\emph{sp}-electron ferromagnets in rock-salt structure, (ii) zincblende
3\emph{d} binary ferromagnets, as well as (iii) ferromagnetic and ferrimagnetic
semi- and full-Heusler compounds.
