Emerging Magnetic Effects of Au Break Junctions with Embedded Ni Nanoparticles

The technological feasibility of spin valve devices containing ferromagnetic nanoparticles depends on the fabrication of clean ohmic contacts that bridge the region between the particle and external electronics. In this paper we use an electrode-narrowing technique to create oxide free contacts on ferromagnetic nanoparticles embedded under gold nanoconstrictions. Constrictions are narrowed with a feedbackbased electromigration method, which reduces the sample conductance to a few multiples of the conductance quantum G o = 2e 2 /h. Magnetoresistance measurements show that hysteresis loops emerge as the constriction conductance decreases towards the conductance quantum. The technique can be used to create ohmic contacts to ferromagnetic nanoparticles for spin-based electronics applications.