Linear complex susceptibility of long range interacting dipoles acted on by thermal agitation and weak external ac fields

TL;DR

This paper derives an analytical formula for the linear complex susceptibility of dipolar assemblies considering thermal agitation, long-range interactions, and weak external fields, revealing how correlation factors influence susceptibility spectra.

Contribution

It introduces a new analytical expression for susceptibility using the forced rotational diffusion equation in the virial approximation, accounting for interaction effects.

Findings

Susceptibility spectrum depends on the Kirkwood correlation factor gK.

For gK > 1, a thermally activated process emerges due to interactions.

For gK < 1, the susceptibility spectrum remains similar to the ideal gas case.

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 gK exceeds unity, a thermally activated process arising from the interaction-specific component arises while for gK<1, the susceptibility spectrum normalized by its static value is practically unaltered with respect to that of the ideal gas phase.