Linear complex susceptibility of long-range interacting dipoles with thermal agitation and weak external ac fields

Abstract

An analytical formula for the linear complex susceptibility of dipolar assemblies subjected to thermal agitation, long-range interactions, and an externally applied uniform sinusoidal field of weak amplitude is derived using the forced rotational diffusion equation of Cugliandolo et al. [Phys. Rev. E 91, 032139 (2015)] in the virial approximation. If the Kirkwood correlation factor of the dipolar assembly ${g}_{K}$ exceeds unity, a thermally activated process arising from the interaction-specific component arises, while for ${g}_{K}<1$ the susceptibility spectrum normalized by its static value is practically unaltered with respect to that of the ideal gas phase.