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Magnetocaloric effect in molecular spin clusters and their assemblies: Exact and Monte Carlo studies using exact cluster eigenstates

Haldar, S and Ramasesha, S (2020) Magnetocaloric effect in molecular spin clusters and their assemblies: Exact and Monte Carlo studies using exact cluster eigenstates. In: Journal of Magnetism and Magnetic Materials, 500 .

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Official URL: https://dx.doi.org/10.1016/j.jmmm.2020.166424

Abstract

Frustrated magnetic molecules are promising alternatives to refrigerant materials for low temperature magnetic refrigeration. We investigate the magnetocaloric effect (MCE) in un-frustrated and frustrated spin clusters formed from spin chains of six sites, with site spins s=1,3/2 and 2 possessing site diagonal anisotropies and anisotropic exchange interactions, using exact diagonalization method. We also study MCE in spin clusters, on a chain, a 2-D square lattice and a 3-D cubic lattice with spin-dipolar interactions by a Monte Carlo method in spin-1 systems which uses exact eigenstates of a cluster. The magnetocaloric effect is closely related to the magnetic Grüneisen parameter �H. In this paper, we compute the magnetic Grüneisen parameter �H, and study its dependence on exchange anisotropy and spin-dipolar interaction. With increase of exchange anisotropy, the maxima in �H shifts to higher magnetic fields and becomes a sharp singularity. The singularities in �H correlate with cusps in the entropy as a function of magnetic field strength, and with crossover in the magnetization in the ground state in isolated clusters. The first maximum in �H shifts to lower fields as we increase spin-dipolar interaction. The first maximum in �H also shifts to lower magnetic field strength as the magnitude of the site spin increases. We show the dependence of �H on the dimensionality of the lattice for a fixed lattice constant.

Item Type: Journal Article
Additional Information: The copyright of this article belongs to Elsevier B.V.
Keywords: Anisotropy; Ground state; Monte Carlo methods; Temperature, Anisotropic exchange interaction; Dipolar interaction; Exact diagonalization method; Exchange anisotropy; Magnetic field strengths; Magnetic molecules; Magnetocaloric effect (MCE); Molecular spin clusters, Magnetocaloric effects
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Depositing User: Id for Latest eprints
Date Deposited: 13 Feb 2020 11:09
Last Modified: 13 Feb 2020 11:09
URI: http://eprints.iisc.ac.in/id/eprint/64470

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