  Magnetic anisotropy phenomena in bimetallic antiferromagnets Mn$_2$Au and
MnIr are studied by first-principles density functional theory calculations. We
find strong and lattice-parameter dependent magnetic anisotropies of the ground
state energy, chemical potential, and density of states, and attribute these
anisotropies to combined effects of large moment on the Mn 3$d$ shell and large
spin-orbit coupling on the 5$d$ shell of the noble metal. Large magnitudes of
the proposed effects can open a route towards spintronics in compensated
antiferromagnets without involving ferromagnetic elements.
