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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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
Publication:	Journal of Magnetism and Magnetic Materials
Publisher:	Elsevier B.V.
Additional Information:	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
Date Deposited:	27 Jan 2020 07:05
Last Modified:	27 Jan 2020 07:05
URI:	http://eprints.iisc.ac.in/id/eprint/64391

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