A study of exchange coupling in NIFE/NIMN bilayers

The effects of annealing time and temperature on the exchange coupling between ferromagnetic (FM) NiFe and antiferromagnetic (AFM) NiMn layers prepared by magnetron sputtering were systematically studied. With both increasing annealing temperature and annealing time, the interfacial exchange coupling energy Jex showed an initial increase followed by a decrease. Magnetic measurement and X-ray diffraction (XRD) analysis revealed that the evolution of Jex should be attributed to the competing of paramagnetic (PM)-AFM phase transition and the interdiffusion across the interfaces caused by annealing. It can be deduced that overannealing, including both too long annealing time and too high annealing temperature, is detrimental to the interfacial exchange coupling. It was also shown that the exchange coupling between NiFe and NiMn layers was thermally very stable. PACS: 75.50