Kondo-like behavior near the metal-to-insulator transition of nanoscale granular aluminum

We show that the normal state transport properties of nanoscale granular aluminum films, near the metal to insulator transition, present striking similarities with those of Kondo systems. Those include a negative magnetoresistance, a minimum of resistance R at a temperature T_m in metallic films, a logarithmic rise at low temperatures, and a negative curvature of R(T) at high temperatures. These normal state properties are interpreted in terms of spin-flip scattering of conduction electrons by local magnetic moments, possibly located at the metal/oxide interfaces.