  We study the tunnel magnetoresistance (TMR) effect and magnetocrystalline
anisotropy in a series of magnetic tunnel junctions (MTJs) with $L1_1$-ordered
fcc ferromagnetic alloys and MgO barrier along the [111] direction. Considering
the (111)-oriented MTJs with different $L1_1$ alloys, we calculate their TMR
ratios and magnetocrystalline anisotropies on the basis of the first-principles
calculations. The analysis shows that the MTJs with Co-based alloys (CoNi,
CoPt, and CoPd) have high TMR ratios over 2000$\%$. These MTJs have
energetically favored Co-O interfaces where interfacial antibonding between Co
$d$ and O $p$ states is formed around the Fermi level. We find that the
resonant tunneling of the antibonding states, called the interface resonant
tunneling, is the origin of the obtained high TMR ratios. Our calculation of
the magnetocrystalline anisotropy shows that many $L1_1$ alloys have large
perpendicular magnetic anisotropy (PMA). In particular, CoPt has the largest
value of anisotropy energy $K_{\rm u} \approx 10\,{\rm MJ/m^3}$. We further
conduct a perturbation analysis of the PMA with respect to the spin-orbit
interaction and reveal that the large PMA in CoPt and CoNi mainly originates
from spin-conserving perturbation processes around the Fermi level.
