MAGNETOSTRICTION AND THERMAL-EXPANSION OF HIGH-TEMPERATURE SUPERCONDUCTORS

Measurements of large magnetostriction (MS) on single crystalline high -T(c) materials (YBa2Cu3Ox and Bi2Sr2CaCu2Ox) are reported. It can be proved that this MS is due to flux line pinning by investigating three typical features: (i) The MS measurements may be fitted with a model which is based on pinning in the critical state. (ii) Cycling the temp erature when measuring the thermal expansion with applied field shows the correlation between MS and flux line distribution. (iii) The relax ation of MS after an applied field is switched off is logarithmic in t ime, similar to j(c).