  We study the tunneling magnetoresistance in the ensembles of ferromagnetic
granules with random easy axes of magnetic anisotropy taking into account the
exchange interaction between granules. It is shown that due to the exchange
interaction magnetoresistance is effectively decoupled from magnetization, i.e.
the strongest negative magnetoresistance can be observed at the field where
magnetization is almost saturated. Under some conditions, the sign of
magnetoresistance can be reversed and tunneling magnetoresistance can become
positive at certain magnetic fields. Our theory agrees with measurements of
magnetoresistance in ensembles of Fe granules in SiCxNy matrix.
