A study of exchange coupling in NIFE/NIMN bilayers

The effects of annealing time and temperature on the exchange coupling betw een ferromagnetic (FM) NiFe and antiferromagnetic (AFM) NiMn layers prepare d by magnetron sputtering were systematically studied. With both increasing annealing temperature and annealing time, the interfacial exchange couplin g energy J(ex) showed an initial increase followed by a decrease. Magnetic measurement and X-ray diffraction (XRD) analysis revealed that the evolutio n of J(ex) should be attributed to the competing of paramagnetic (PM)-AFM p hase transition and the interdiffusion across the interfaces caused by anne aling. It can be deduced that overannealing, including both too long anneal ing time and too high annealing temperature, is detrimental to the interfac ial exchange coupling. It was also shown that the exchange coupling between NiFe and NiMn layers was thermally very stable. PACS: 75.50 (C) 2000 Elsev ier Science S.A. All rights reserved.