Shock-loading effects on superconductivity of HgBa₂CuO_y

We have investigated shock-loading effects on the structural and superconducting properties of a high-T_c superconducting oxide HgBa₂CuO_y (Hg-1201) by X-ray powder diffraction analysis, magnetic measurements and electron microscopy. Most of the shock experiments were performed using samples with pre-cooling to liquid nitrogen temperature in order to prevent decomposition due to temperature rise. The width of magnetization hysteresis (ΔM) of Hg-1201 was reduced by shock-loading, but it recovered and improved by subsequent appropriate annealing. The magnetization hysteresis loops and TEM observation indicate that this improvement of ΔM is probably caused by defects as pinning centers which were introduced by shock-loading and preserved by the annealing. The present study demonstrates that the pre-cooled shock-loading method is effective for introducing pinning centers into high-T_c superconductors, even for the composition including a volatile element such as Hg.