Magnetic susceptibility of nanoscale Kondo systems

The mesoscopic Kondo effect in metallic nanoparticles containing a magnetic impurity is investigated by model calculations. A Maxwell–Garnett approach is used to approximately determine the resistivity of doped nanoparticles in a matrix, and the magnetic susceptibility is estimated from the confinement of the conduction electrons. Conductivity measurements of nanoparticles embedded in a matrix are difficult to realize, because metallic matrices distort the Kondo cloud, whereas insulating or semiconducting matrices yield a very weak signal. By comparison, susceptibility measurements do not suffer from these shortcomings. The Kondo effect survives in nanoparticles even if the cluster size is much smaller than the Kondo screening cloud, but the effective Curie constant becomes constant below a particle-size dependent transition temperature and the temperature dependence of the susceptibility is no longer universal