Abstract:
The effect of He ion irradiation on the magnetic properties of NiFe exchange coupled to different
antiferromagnetic alloys (FeMn, CrMn, and PtMn) with the same layer thickness is investigated. All
systems exhibit an enhanced coercivity prior to irradiation. An exchange bias field is only observed
for FeMn and PtMn. Upon ion irradiation the FeMn-based system shows with increasing ion dose
an enhancement followed by a decrease and finally a full suppression of the exchange bias field. For
systems exchange coupled to PtMn only a decrease and suppression of the bias field is found. This
can be attributed to the ion induced chemical disordering of the antiferromagnetic phase in the latter
case. In the case of CrMn the antiferromagnetic layer thickness is too small to induce an exchange
bias field, but an enhanced coercivity is observed which is caused by the exchange coupling between
the antiferromagnetic and ferromagnetic layers. For all systems, this enhanced coercivity of the
exchange coupled bilayer system is modified by ion irradiation.
