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Field dependent anisotropic
magnetoresistance measurements on CoFe/IrMn
bilayers
Heather L. Brown and E. Dan Dahlberg, Mark Kief and Chunhong Hou
The exchange anisotropy field, along with the qualitative distribution of the local pinning field at the
ferromagnetic/antiferromagnetic interface, has been studied in polycrystalline CoFe/IrMn bilayers. The exchange
anisotropy was studied using both the anisotropic magnetoresistance (AMR) technique and hysteresis loop
measurements. The AMR technique determines a larger value for the exchange anisotropy than the hysteresis loop
technique. It is observed that Hea extracted via the AMR technique for the majority of samples shows a
quantifiable dependence on the applied measurement field, even at fields much less than the exchange bias
measured by hysteresis loop. It is believed that a reversible measurement of the soft dispersive moments takes
place at these low fields, and that the field dependence is indicative of a distribution of the local
magnetization direction.