AC susceptibility measurements: a quality test for high-T(C) superconducting bulk materials

Temperature dependent measurements of high T(c) bulk material reflect the quality of the high T(c) grains and the intergranular weak links. Besides, ac field dependent measurements give access to a quantitative quality label of the bulk material : its critical current density J(c). Herefore critical state models as the Bean and the Kim model are used. Our measurements on long orthorombic samples with different cross sections a x b show that the Kim model is the most realistic one. It leads to a b/a independent average value of J(c), which equals the J(c) value of transport measurements and of magnetic SQUID measurements at low dc fields