Nonlinear response of superparamagnets with finite damping: an analytical approach

TL;DR

This paper presents an analytical method to understand the nonlinear magnetic response of superparamagnets with finite damping, providing formulas that match exact solutions and aid experimental data modeling.

Contribution

It introduces a simple approximate expression for nonlinear susceptibility of superparamagnets, derived from balance equations, aligning well with exact solutions.

Findings

Analytical expression matches exact solutions

Method aids in modeling experimental data

Helps determine damping coefficients

Abstract

The strongly damping-dependent nonlinear dynamical response of classical superparamagnets is investigated by means of an analytical approach. Using rigorous balance equations for the spin occupation numbers a simple approximate expression is derived for the nonlinear susceptibility. The results are in good agreement with those obtained from the exact (continued-fraction) solution of the Fokker-Planck equation. The formula obtained could be of assistance in the modelling of the experimental data and the determination of the damping coefficient in superparamagnets.