ELECTROMAGNETIC SHIELDING PROPERTIES OF YTTRIUM BARIUM CUPRATE SUPERCONDUCTOR

There is evidence that electromagnetic radiation can penetrate into solid samples of yttrium barium cuprate superconductors at magnetic flux densities of less than 1 mT. We have previously shown how this behavior may lead to potentially useful inductive effects, but the penetration of flux is an obvious disadvantage for magnetic shielding applications. We describe here a technique for the quantitative measurement of the effectiveness of these materials as magnetic shields. We report the dependence of the shielding factor on sample microstructure, density, thickness, field strength, temperature and frequency. The technique provides a quick, reliable, non-contact means of establishing the 'quality' of a sample which correlates well with other properties such as the Meissner fraction, critical current density and long-term stability.