Physical origin of decrease in exchange coupling in Ga+ ion irradiated CoFe/IrMn films
(School of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China)
Abstract: The physical properties of a CoFe/IrMn exchange-coupled bilayer submitted to 30keV Ga+ ion irradiation in a focused ion beam machine as a function of irradiation dose were studied by using various imaging and analy- tical techniques including high resolution TEM and spectrum imaging based on electron energy loss spectroscopy to better understand why the magnetic properties can be modified. When the ion dose increases the irradiation initially induces grain growth and subsequently element mixing and amorphisation, which can be largely accounted for by a simple ballistic recoil mechanism model. The modification of the microstructure and the interfacial mixing of atoms between the various layers results in the continuous reduction in the exchange field and the coercivity of IrMn/CoFe bilayers.
Key words: CoFe/IrMn film； Ga+ ion irradiation； physical properties； exchange coupling