Abstract
The consequences of a hierarchical model for barrier heights between metastable states are explored. We show that the Parisi physical order parameter P(q) extracted from the equilibrium out-of-phase susceptibility, is consistent with previous de measurement of P(q). The dynamic susceptibility χ″(ω, t) before and after a dc magnetic field change is obtained by introducing a reduction of barrier heights by the relative Zeeman energy change E z, the reduction increasing for increasing barrier height. This results in the correct frequency dependence for the observed jump in χ″(ω) upon a change in magnetic field. Measurement of these jumps over a wide range of waiting times serves as a vehicle for the determination of excitation barrier response to a magnetic field change.