Susceptibility of superconductor disks and rings with and without flux creep

First some consequences of the Bean assumption of constant critical current Jc in type-II superconductors are listed and the Bean ac susceptibility of narrow rings is derived. Then flux creep is described by a nonlinear current-voltage law E(proportional to)J(n), from which the saturated magnetic moment at constant ramp rate H-a(t) is derived for rings with general hole radius a(1) and general creep exponent n. Next the exact formulation for rings in a perpendicular applied field H-a(t) is presented in the form of an equation of motion for the current density in thick rings and disks or the sheet current in thin rings and disks. This method is used to compute general magnetization curves m(H-a) and ac susceptibilities chi of rings with and without creep, accounting also for nonconstant J(c)(B). Typical current and field (B) profiles are depicted. The initial slope of m(H-a) (the ideal diamagnetic moment) and the field of full penetration are expressed as functions of the inner and outer ring radii al and a. A scaling law is derived which states that for arbitrary creep exponent n the complex nonlinear ac susceptibility chi(H-0,omega) depends only on the combination H-0(n-1)/omega of the ac amplitude H-0 and the ac frequency omega/2 pi. This scaling law thus connects the known dependencies chi = chi(omega) in the ohmic limit(n = 1) and chi = chi(H-0) in the Bean limit (n --> infinity).