  We employ the recently discovered antiferromagnetic tunneling anisotropic
magnetoresistance to study the behavior of antiferromagnetically ordered
moments in IrMn exchange coupled to NiFe. Experiments performed by common
laboratory tools for magnetization and electrical transport measurements allow
us to directly link the broadening of the NiFe hysteresis loop and its shift
(exchange bias) to the rotation and pinning of antiferromagnetic moments in
IrMn. At higher temperatures, the broadened loops show zero shift which
correlates with the observation of fully rotating antiferromagnetic moments
inside the IrMn film. The onset of exchange bias at lower temperatures is
linked to a partial rotation between distinct metastable states and pinning of
the IrMn antiferromagnetic moments in these states. The observation complements
common pictures of exchange bias and reveals the presence of an electrically
measurable memory effect in an antiferromagnet.
