AC-LOSS VALLEY IN TYPE-II SUPERCONDUCTORS

Hysteresis losses W have been calculated as a function of temperature T, bias field H(b), and amplitude h0 for planar geometry in the critical-state framework with j(c) = alpha(T)/B(n) for n = 0, 1/2, and 1 in the range H(b)/h0 less-than-or-similar-to 2. Chi(max), the maximum of the ac susceptibility, chi(ac) = W/pi-mu(0)h(0)2 versus T/T(c) for various h(0), H(b), and alpha(T) are seen to trace a "universal" ac-loss valley for each n with 0 < n less-than-or-equal-to 1 when plotted versus H(b)/h0. T(max) corresponding to chi(max) graphed versus H(b)/h0 has a peak whose position differs significantly from that of the minimum in the ac-loss valley. chi(ac) at the onset of full penetration, denoted chi*, and the corresponding T, denoted T*, are seen to deviate markedly from chi(max) and T(max) in all these circumstances.