Alexey O. Ivanov | Searcharxiv

arXiv2023

Role of ionic surfactant in magnetic dynamics of self-assembled dispersions of nanoplatelets

In complex colloidal systems, interparticle interactions strongly affect the dynamics of the constituting particles. A study of the dynamical response also provides invaluable information on the character of those interactions. Here we demonstrate how tuning the electrostatic interactions by an ionic surfactant in dispersions of magnetic nanoplatelets leads to developing new dynamic modes in magnetic response spectra. The collective modes can be induced or suppressed by either varying the concentration ratio of the magnetic nanoplatelets (MP) to the surfactant or increasing the MP concentration reflecting the nanoscale characteristics of this fluid magnet.

cond-mat.soft↗

arXiv2020

Thermodynamics of interacting single-domain superparamagnetic nanoparticles frozen in the nodes of a regular cubic lattice

In this work, we study the effect of dipole-dipole interparticle interactions on the static thermodynamic and magnetic properties of an ensemble of immobilized monodisperse superparamagnetic nanoparticles. We assume that magnetic nanoparticles are embedded in the nodes of a regular cubic lattice, so that the particle translational degrees of freedom are turned off. The relaxation of the magnetic moments of the nanoparticles occurs by the Neel mechanism. The easy axes are aligned (i) parallel or (ii) perpendicular to the direction of an external field. These models are investigated using theory and computer simulation, taking microscopic discrete structure explicitly into account. The analytical expressions of the Helmholtz free energy, the static magnetization, and the initial magnetic susceptibility are derived for both configurations (i) and (ii) as functions of the height of the magnetic crystallographic anisotropy energy barrier, measured by parameter $σ$, and the intensity of the dipole-dipole interparticle interactions measured by $λ_e$. A good agreement between the theory and the results of MC simulations in the region of low and moderate values of $λ_e$ and $σ$ is obtained. For high values of $λ_e$ and $σ$, the structuring of magnetic moments in regularly orientated structures was found from MC simulations for configuration (i).

cond-mat.mtrl-sci↗