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A computational perspective on magnetic coupling, magneto-structural correlations and magneto-caloric effect of a ferromagnetically coupled {Gd-III-Gd-III} pair

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Title A computational perspective on magnetic coupling, magneto-structural correlations and magneto-caloric effect of a ferromagnetically coupled {Gd-III-Gd-III} pair
 
Creator RAJESHKUMAR, T
SINGH, SK
RAJARAMAN, G
 
Subject SMMs
MCE
DFT calculations
Magnetic coupling in {4f-4f}
{Gd-III-Gd-III} pair
Magneto-structural correlations
SINGLE-MOLECULE MAGNETS
TRANSITION-METAL-COMPLEXES
CHAIN MAGNETS
POLYNUCLEAR COMPLEXES
LANTHANIDE COMPLEXES
EXCHANGE INTERACTION
CLUSTERS
REFRIGERATION
CONSTANTS
TIME
 
Description Density functional calculations have been performed on a dinuclear (Gd-III-Gd-III) complex [{Gd(OA-c)(3)(H2O)(2)}(2)]center dot 4H(2)O (1) which has recently been reported to have a very large MCE [M. Evangelisti, O. Roubeau, E. Palacios, A. Camon, T.N. Hooper, E.K. Brechin, J.J. Alonso, Angew. Chem., Int. Ed. 50 (2011) 6606]. The focus here is (i) to asses a suitable functional within DFT framework to compute good numerical estimate of J values (ii) to probe the mechanism of coupling between the two Gd-III ions via computational means (iii) to develop magneto-structural correlations to relate the sign and strength off to specific structural parameter and (iv) to conceive the origin of large magneto-caloric effect (MCE) observed. Testing a series of functionals and a set of basis sets, it is evident that the hybrid B3LYP functional behaves marginally well over others with a combination of SARC basis set incorporating ZORA (zeroth-order regular approximation) relativistic effect for the Gd-III ions. The MO and NBO tools have been utilized to probe the mechanism of coupling and this reveals that there are two contributions. The first is charge transfer in nature leading to a ferromagnetic contribution due to the involvement of empty 6s/5d/6p orbitals of Gd-III ions and the second contribution is due to 4f-4f orbital overlap and this adds to both ferro and antiferromagnetic part of the exchange. In 1, the ferromagnetic contribution prevails over the other leading to a net ferromagnetic J. The developed magneto-structural correlations reveal that the Gd-O-Gd angle is an important parameter as it switches the coupling from ferro to antiferro at lower angles. A weak intermolecular ferromagnetic interaction mediating via H-bonding interaction results in a ferromagnetic interaction at low temperatures and hence a large MCE. (C) 2012 Elsevier Ltd. All rights reserved.
 
Publisher PERGAMON-ELSEVIER SCIENCE LTD
 
Date 2014-10-15T12:19:14Z
2014-10-15T12:19:14Z
2013
 
Type Article
 
Identifier POLYHEDRON, 521299-1305
http://dx.doi.org/10.1016/j.poly.2012.06.017
http://dspace.library.iitb.ac.in/jspui/handle/100/14887
 
Language en