Kondo-like effect in the resistivity of superparamagnetic cluster-layered Fe/Cr nanostructures

The magnetic and magnetoresistive properties of nanostructured Fe/Cr multilayers with ultrathin Fe layers (the nominal Fe thickness tFetFe is down to 0.3Å) were investigated at low temperatures (down to 4.2 K) in magnetic fields up to 90 kOe. Nanostructures were MBE grown in ultrahigh vacuum on single crystal MgO substrates. It is shown that Fe layers in nanostructures with tFe<2Å are not continuous but consist of separate ferromagnetic clusters. Such cluster-layered nanostructures exhibit the superparamagnetic properties and the Kondo-like behavior of the resistance.