Interaction effects in heterostructures of nanoscale magnetic particles and magnetic thin films

Elongated magnetic nanoparticles attract continuing attention because of potential technological applications. STM assisted CVD is an advantageous fabrication technique for exact positioning of individual Fe particles (diameter 5 -- 20 nm) on different substrate materials. A first step towards an application of these small and local magnetic flux sources to intentionally influence and investigate other materials is to study structures of magnetic particles grown onto an underlying magnetic film. This enhances interaction effects between adjacent particles. Also, the particles alter the magnetic domain structure of the thin film making the transport properties of the latter sensitive to the magnetization state of the particles grown on top leading to a distinct switching effect in the magnetoresistance that persists up to room temperature. The interaction effects in such magnetic particles/thin-film heterostructures are further investigated in a device with a single magnetic nanoparticle and an underlying film of the concentrated magnetic semiconductor EuS. The magnetic interaction of this system can be tuned by sweeping the temperature through T$_{C}$ of EuS. We discuss the heterostructure's magnetization behavior in terms of different magnetic interaction strengths.