Magnetostriction of HTSC single crystals

Abstract

We have measured the sample length change of HTSC single crystals in the superconducting state in a magnetic field. The magnetic field was applied parallel to the crystallinec-axis direction and was swept at a constant rate of 10 mT/s up to 6 T. The sample length change was measured along theab-plane direction, i.e., perpendicular to the field. We have found for the Bi₂Sr₂CaCu₂O₈ single crystals that the relative sample length change (ΔL/L) is extraordinarily large for a superconductor, on the order of 10⁻⁴. For the case of (La_1−x Sr _x )₂CuO₄, the amount of magnetostriction was not as large as for the Bi system, but the magnetostriction curves had many similarities. For both compounds, a relaxation phenomenon was observed when the field sweep was suspended at a certain field value. These observations are discussed in relation to flux line pinning.