Dependence of complex permeability and harmonic power generation of a sintered YBa2Cu3O7-δ rod on applied AC and DC magnetic fields

Systematic experimental studies are reported for the AC permeability and harmonic generation power Pnf in a sintered rod of granular YBa2Cu3O7-δ at 77 K as a function of simultaneously applied AC and DC magnetic fields from 0.01 to several hundred Oe. The separate contributions of the inter- and intragranular supercurrents are quite clearly resolved, enabling the development of a generalized critical state model, which with two components is found to well explain the AC permeability and harmonic generation power as functions of AC and DC fields up to the n = 9 harmonic. Intergranular currents dominate the behavior for fields less than about 50 Oe; Intragranular currents dominate for fields greater than 100 Oe. (orig.)