Magnetic microstructures created by local interface mixing

Magnetic micro- and nanostructures are of great interest due to the fundamental physics involved if the dimension is shrunk as well as due to the application potential in storage, sensing and logic devices. For the creation of such structures typically lithography is used in combination with either etching or lift-off processes. In both cases the magnetic element is defined by isolated topographic structures. An alternative approach relies on the local ion irradiation of a magnetic multilayer structure. As a result of the ion irradiation an interfacial mixing between ferromagnetic layers and non-magnetic interlayers is achieved which consequently reduce and finally fully suppress the ferromagnetism. In order to demonstrate this behaviour Ni80Fe20/Ta multilayers with a different number of repetitions are used. The structural and magnetic properties are investigated by x-ray reflectivity and magneto-optic Kerr effect magnetometry as a function of noble gas irradiation fluence and number of multilayer repetitions. The experimental results are accompanied by TRIDYN simulations. In addition magnetic microstructures are created by means of large area ion irradiation through lithographically defined masks. By choosing the irradiation fluence the exchange coupling between the microstrucutres can be switching on and off. The magnetic domain configuration in these elements is imaged by means of Kerr microscopy and magnetic force microscopy. Thus the modified magnetization reversal curves can be interpreted on the basis of the micromagnetic domain structure.