Coupling of Fe and Uncompensated Mn Moments in Exchange-Biased Fe/MnPd

A bilayer exchange-bias system composed of Fe/MnPd is investigated using x-ray magnetic circular dichroism (XMCD) and soft x-ray resonant magnetic reflectometry (XRMR). The absorption and XMCD data at the Fe L and Mn L edges are used to derive the optical and magneto-optical properties of the individual layers. Then the structural and magnetic depth profiles of the sample are obtained from XRMR. From reflectivity measurements at the Fe L and Mn L edges, a precise magnetic depth profiling of the interface region between the ferromagnet (F) and antiferromagnet (AF) was carried out. It reveals rotatable and pinned uncompensated Mn moments in the AF. By comparing the signs and magnitudes of the absorption, the relative coupling directions in the system are determined. It is found that rotatable Mn and the ferromagnetic Fe couple anti-parallel. The pinned Mn moments are oriented antiferromagnetic to the neighboring rotatable Mn and ferromagnetic with respect to the Fe during the field cooling process.