GIANT MAGNETOSTRICTION IN BI2SR2CACU2O8 SINGLE-CRYSTAL IN THE SUPERCONDUCTING STATE AND ITS MECHANISM

Unusually large magnetostriction for a superconductor was found in a single crystal of the high-T(c) cuprate Bi2Sr2CaCu2O8. The sample length change was measured along the ab plane under magnetic fields applied up to 6 T paxallel to the c axis. The sample decreased in length during the field increasing process and with relative change exceeding 10(-4) at 4.8 K. A quantitative model has been proposed which accounts for the magnetostriction in terms of internal forces arising from flux pinning. These observations show that magnetostriction measurement is a novel and unique technique to investigate the pinning effect and related phenomena in type-II superconductors.