  We present results of the magneto-crystalline anisotropy energy (MAE)
calculations for chemically ordered $L1_0$ CoPt and FePt alloys taking into
account the effects of strong electronic correlations and spin-orbit coupling.
The local spin density + Hubbard U approximation (LSDA+U) is shown to provide a
consistent picture of the magnetic ground state properties when intra-atomic
Coulomb correlations are included for both 3$d$ and 5$d$ elements. Our results
demonstrate significant and complex contribution of correlation effects to
large MAE of these material.
