Dynamics of particles with cubic magnetic anisotropy in a viscous liquid

TL;DR

This paper models the specific absorption rate of cubic-anisotropy iron nanoparticles in viscous liquids, revealing different magnetization reversal modes and showing higher SAR compared to uniaxial nanoparticles, with validity limits for linear response theory.

Contribution

It introduces a stochastic modeling approach for particles with cubic anisotropy in viscous liquids, highlighting distinct reversal modes and enhanced SAR performance.

Findings

Viscous and magnetic reversal modes depend on magnetic field amplitude.

SAR exceeds that of uniaxial nanoparticles at similar conditions.

Linear response theory applies only at low magnetic fields (<70 Oe).

Abstract

The specific absorption rate (SAR) of a dilute assembly of spherical iron nanoparticles with cubic anisotropy distributed in a viscous liquid is calculated using the solution of stochastic Landau - Lifshitz equation for unit magnetization vector and stochastic equations for multiple particle directors that specify the spatial orientation of the nanoparticle in a liquid. The viscous and magnetic magnetization reversal modes of particles are revealed at low and sufficiently high amplitudes of alternating magnetic field, respectively. The SAR of iron nanoparticle assembly is shown to exceed significantly that of iron oxide nanoparticles with uniaxial anisotropy at the same amplitudes and frequencies of applied magnetic field. The linear response theory is shown to be valid only at small magnetic field amplitudes, H0 < 50 - 70 Oe.