Magnetic and superconducting properties of metal and oxide nanoclusters on biological templates

Nanogranular materials will play an important role in future technologies due to their exciting magnetic and superconducting properties that differ strongly from their bulk counterparts. In this study, we have focused on metal and oxide nanoclusters that have been deposited on a biological template, a self-assembling surface layer (S-layer) of Bacillus sphaericus JG-A12 which is composed of identical monomers. We present data of Pd, Pb, and Fe₃O4 nanograins with sizes of 2, 19, and 13 nm respectively. The magnetization data obtained for the palladium clusters demonstrate that the Stoner enhancement factor of the d conduction-electron susceptibility is clearly reduced compared to the one of bulk Pd. For the Pb nanograins we have investigated the superconducting B-T phase diagram and encountered a superconducting critical field of the size of several Tesla which is strongly enhanced in comparison to the corresponding critical magnetic field of 0.09 T for bulk Pb. Last but not least we investigated the superparamagnetic properties of Fe₃O4 nanograins and have found a magnetic anomaly at 30 K. Here, we present magnetization data taken by SQUID magnetometry as well as experimental results of dielectric measurements.