Nonlinear ac stationary response and dynamic magnetic hysteresis of quantum uniaxial superparamagnets

TL;DR

This paper investigates the nonlinear ac magnetic response and hysteresis behavior of quantum uniaxial superparamagnets with varying spin numbers, revealing quantum effects on their dynamic magnetic properties.

Contribution

It provides a comprehensive quantum mechanical analysis of nonlinear ac response and hysteresis in superparamagnets, extending understanding beyond classical models.

Findings

Nonlinear response strongly depends on quantum spin number S.

Harmonic components and hysteresis loops are quantitatively characterized.

Results align with classical solutions in the linear response limit.

Abstract

The nonlinear ac stationary response of uniaxial paramagnets and superparamagnets - nanoscale solids or clasters with spin number S ~ 10^0 - 10^4 - in superimposed uniform ac and dc bias magnetic fields of arbitrary strength, each applied along the easy axis of magnetization, is determined by solving the evolution equation for the reduced density matrix represented as a finite set of three-term differential-recurrence relations for its diagonal matrix elements. The various harmonic components of the magnetization, dynamic magnetic hysteresis loops, etc. are then evaluated via matrix continued fractions indicating a pronounced dependence of the nonlinear response on S arising from the quantum spin dynamics. In the linear response approximation, the results concur with existing solutions.