Abstrakt
We report the observation of cluster ( local) superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O-3 ceramics prepared at a hydrostatic pressure of 6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The superconductivity is manifested by an abrupt drop of the magnetic susceptibility at the critical temperature T-c approximate to 7 K.
Both the magnitude of this drop and T-c decrease with magnetic field increase. Similarly, the low-field paramagnetic absorption measured by EPR spectrometer drops significantly below T-c as well.
The observed effects and their critical magnetic field dependence are interpreted as manifestation of the superconductivity and the Meissner effect in metallic Pb nanoclusters existing in the ceramics. Their volume fraction and average size were estimated as 0.1-0.2% and 140-150 nm, respectively.
The superconductivity related effects disappear after oxidizing annealing of the ceramics.