Interfacial exchange coupling in Fe-Tb/[Co/Pt] heterostructures

The exchange interaction and magnetization reversal processes in exchange-biased heterostructures consisting of amorphous ferrimagnetic Fe-Tb alloy films and ferromagnetic Co/Pt multilayers were investigated. Both film systems exhibit an easy axis magnetization perpendicular to the film plane. The dependence of the interfacial exchange coupling on the stoichiometry of the Fe-Tb layer as well as the number of repetitions in the Co/Pt multilayers were analyzed. The net magnetization and effective magnetic anisotropy of the Fe-Tb alloy films have an influence on the exchange energy per unit area. A large exchange-bias field up to 8 kOe is found to be accompanied by an interfacial domain wall as probed by element specific x-ray magnetic circular dichroism absorption measurements. This domain wall exhibits a total thickness between 3 and 4 nm and affects strongly the magnetization reversal in the heterostructure. Furthermore, a linear relation between the thickness of the ferromagnetic Co/Pt multilayers and the exchange-bias field is observed and can be attributed to a change of the location where the interfacial domain wall nucleates in the heterostructure. DOI: 10.1103/PhysRevB.87.054415