Anomalous magnetization process in exchange-biased MnPd/Co bilayers (original) (raw)

2003, Physica B-condensed Matter

MnPd/Co bilayers sputtered onto Si (1 0 0) substrates with varied MnPd thickness have been investigated. Structural characterization of the bilayers was carried out with an X-ray diffractometer and their magnetic properties were measured by a vibrating-sample magnetometer. As-deposited bilayers exhibit large but quite usual exchange-biased coupling, i.e. the shift of the hysteresis loop towards the field direction opposite to the cooling-field direction. This exchange bias vanishes if the antiferromagnetic (AFM) layer thickness is below a certain value. However, for annealed bilayers with an MnPd layer thickness below a critical value, large exchange bias and asymmetric double-shifted loops are unexpectedly observed when the measuring field is along the cooling-field direction. These anomalies in the magnetization process can be explained if one postulates that the orientation of the AFM easy axis with respect to the spin direction of the ferromagnetic layer is changed when the thickness of the AFM layer decreases. r