Optically induced changes in the magnetic properties of the ceramic superconductorLa1.8Ba0.2CuO4

Optically induced changes have been observed in the magnetic properties of the ceramic superconductor ${\mathrm{La}}_{1.8}$ ${\mathrm{Ba}}_{0.2}$ ${\mathrm{CuO}}_4$. The most prominent feature of our data is the light-induced change of the magnetic moment, proportional to ${\mathit{T}}^{\mathrm{-}1/2}$exp(a/kT), where a is a constant when the sample is cooled below ∼${\mathit{T}}_{\mathit{c}}$/2. Results obtained in applied magnetic fields of 1, 9, and 26 Oe suggest that the observed effect has contributions from a weakening of the intergranular Josephson junctions under illumination as well as from an additional form of optically induced flux creep, which depends on the applied magnetic field.