Magnetocaloric effect in molecular spin clusters and their assemblies: model exact and Monte Carlo studies

TL;DR

This study investigates the magnetocaloric effect in small spin clusters and their assemblies across various dimensions, using exact and Monte Carlo methods to analyze how anisotropy, dipolar interactions, and dimensionality influence magnetic properties.

Contribution

It provides a comprehensive analysis of the magnetocaloric effect in spin clusters and assemblies, highlighting the effects of anisotropy, dipolar interactions, and dimensionality with both exact and Monte Carlo approaches.

Findings

Maxima in the magnetic Grüneisen parameter shift with anisotropy and dipolar interactions.

Behavior of the Grüneisen parameter correlates with changes in magnetic entropy.

Dimensionality affects the magnetic response and Grüneisen parameter behavior.

Abstract

We study the magnetocaloric effect (MCE) in spin clusters of six spins with site spins $s=1$, $3/2$ and $2$ for different exchange anisotropies. We also study MCE in an assembly of spin clusters, on a chain, a 2-D square lattice and 3-D cubic lattice with spin-dipolar interactions using a Monte Carlo method in spin-1 systems. We compute the magnetic Gr\"uneisen parameter $\Gamma_H$, and study its dependence on exchange anisotropy and spin-dipolar interaction. With increase of exchange anisotropy the maxima in $\Gamma_H$, shifts to higher magnetic fields and becomes a sharp singularity. The first maximum in $\Gamma_H$ shifts to lower fields as we increase spin-dipolar interaction. The behaviour of $\Gamma_H$ on applied magnetic field is also reflected in the magnetic entropy of the systems. The first maximum in $\Gamma_H$ also shifts to lower magnetic field strength as the magnitude of the site spin increases. We also show the dependence of $\Gamma_H$ on dimensionality of the lattice for a fixed lattice constant.