The Role of Interfaces in CoFe/IrMn Exchange Biased Systems

A trilayer system consisting of an IrMn layer exchanged coupled to two CoFe layers of equal thickness has been studied. A single stage reversal was observed over a wide range of temperatures. Two bilayers with the same thicknesses of the pinning layer but different ferromagnetic thicknesses were also studied. By comparing the magnetic properties of these three stacks the effect of the interfacial area on the exchange field and the coercivity has been determined. We find that the interfacial area has a very minor effect on the exchange field H_ex and the blocking temperature (T_B) but causes a doubling of the coercivity (H_c). This indicates that H_c is dominated by the interface whereas the exchange bias is controlled by volumetric effects