  We report on simulations in general relativity of magnetized disks onto black
hole binaries. We vary the binary mass ratio from 1:1 to 1:10 and evolve the
systems when they orbit near the binary-disk decoupling radius. We compare
(surface) density profiles, accretion rates (relative to a single, non-spinning
black hole), variability, effective $\alpha$-stress levels and luminosities as
functions of the mass ratio. We treat the disks in two limiting regimes: rapid
radiative cooling and no radiative cooling. The magnetic field lines clearly
reveal jets emerging from both black hole horizons and merging into one common
jet at large distances. The magnetic fields give rise to much stronger shock
heating than the pure hydrodynamic flows, completely alter the disk structure,
and boost accretion rates and luminosities. Accretion streams near the horizons
are among the densest structures; in fact, the 1:10 no-cooling evolution
results in a refilling of the cavity. The typical effective temperature in the
bulk of the disk is $\sim 10^5 (M/10^8 M_\odot)^{-1/4} (L/L_{\rm edd})^{1/4}
{\rm K}$ yielding characteristic thermal frequencies $\sim 10^{15} (M/10^8
M_\odot)^{-1/4} (L/L_{\rm edd})^{1/4}(1+z)^{-1}{\rm Hz} $. These systems are
thus promising targets for many extragalactic optical surveys, such as LSST,
WFIRST, and PanSTARRS.
