Low field magnetization measurements on single crystals of superconducting YBa2Cu3O7-δ

Abstract
Low field (H ≤ 3G) magnetization measurements have been performed on small single crystals of superconducting YBa2Cu3O7-δ (Tc ≃ 95K) using a SQUID magnetometer. They revealed anisotropic properties in the temperature dependence of the magnetization. The Meissner effect (always smaller than 10 % ) is 2 to 3 times larger along the c direction than along one of the perpendicular directions. A sharp unique transition at 95K is observed with the field parallel to c. In the perpendicular direction a second transition line seems to be crossed at T = 84K with an applied field of 3G. In all three crystals studied, a very small ferromagnetic polarization, pointing approximately along the c direction, is observed