  An isotropic medium, having magnetic sublevels, when subjected to a magnetic
field or an electromagnetic field can induce anisotropy in the medium; and as a
result the plane of polarization of the probe field can rotate. Therefore the
rotation due to the magnetic field alone, can be {\em controlled efficiently}
with use of a coherent field. We show, using a control field, significant
enhancement of the magneto-optical rotation and demonstrate the possibility of
realizing {\em magneto-optical switch}.
