We present the results of a study of the magnetic properties of an array of 34-nm thick Co(100) epitaxial ring magnets, with inner and outer diameters of d(in) = 1.3 microm and d(out) = 1.6 microm, respectively. Magnetic measurements and micromagnetic simulations show that a two step switching process occurs at high fields, indicating the existence of two different stable states. In addition to the vortex state, which occurs at intermediate fields, we have identified a new bi-domain state, which we term the onion state, corresponding to opposite circulation of the magnetization in each half of the ring. The onion state is stable at remanence and undergoes a simple and well characterized nucleation free switching.

We have developed a simple process to fabricate high-TC Josephson junctions by a combination of focused ion beam milling and 100 keV H2+ ion implantation. The resistively shunted junction-like current–voltage characteristics were observed in the temperature range of 48 to 4.2 K. The devices showed clear dc and ac Josephson effects. This technique is very promising in terms of simplicity and flexibility of fabrication and has potential for high-density integration.

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