Vectorial mapping of exchange anisotropy in IrMn/FeCo multilayers using the reversible susceptibility tensor

A method for probing exchange anisotropy based on reversible susceptibility tensor is proposed. The experimental results obtained on exchange biased IrMn/FeCo multilayers are supported by the theoretical analysis of the transverse and longitudinal susceptibilities in the case of exchange-coupled systems. The vectorial mapping of the exchange bias in the studied sample is performed by detecting a composite signal containing both transverse and longitudinal susceptibilities for different orientations of the applied field. This procedure, that is demonstrated both theoretically and experimentally, allows one to obtain the critical curve of the switching fields. The critical curve constitutes the fingerprint of the switching processes from which both magnitude and direction of the directional anisotropy can be determined.