VECTOR MAGNETIZATION STUDIES OF ANISOTROPIC SUPERCONDUCTORS

The irreversible magnetic moment Delta m(ab) associated with fields ap plied parallel to the ab-plane of high-temperature superconductor (HTS ) crystals provides a crucial measure of the inter-layer coupling. How ever, because these materials are so anisotropic, Delta m(ab) is small , and easily overwhelmed by the magnetization associated with in-plane screening currents. We show that even in the feast anisotropic HTS ph ase, YBa2Cu3O7, the field alignment with the ab-planes has to be withi n a fraction of a degree for Valid data on Delta m(ab) to be obtained. Furthermore, slight mis-positioning of the sample in the magnetometer sense coils can cause serious artefacts. The addition of a second sig nal channel to the magnetometer, in which the magnetic moment perpendi cular to the applied field is also monitored, allows accurate alignmen t and enables reliable measurements of Delta m(ab) to be made.