Magnetocaloric effect in M-pyrazole-[Nb(CN)_{8}] (M=Ni, Mn) molecular compounds

doi:10.1088/0953-8984/24/50/506002

Magnetocaloric effect in M-pyrazole-[Nb(CN)_{8}] ...

Bibliographic description

punktacja MNiSW [2012 A]: 30

title:	Magnetocaloric effect in M-pyrazole-[Nb(CN)_{8}] (M=Ni, Mn) molecular compounds
author:	Fitta Magdalena, Bałanda Maria, Mihalik Marian, Pinkowicz Dawid , Sieklucka Barbara , Zentkova Maria, Pełka Robert
Journal title:	Journal of Physics. Condensed Matter
volume:	24
issue:	50
date of publication:	2012
article ID:	506002
ISSN:	0953-8984
eISSN:	1361-648X
DOI:	10.1088/0953-8984/24/50/506002
language:	English
Journal language:	English
abstract in english:	We report a study of magnetocaloric effect (MCE) in cyanido-bridged {[MII(pyrazole)4]2[NbIV(CN)8]⋅4H2O}n molecular compounds where M = Ni, Mn, pyrazole = C3H4N2. The substances show a sharp phase transition to a long range magnetically ordered state, with ferromagnetic coupling between M and Nb sublattices in the case of the Ni-based sample 1 (Tc = 13.4 K) and ferrimagnetic coupling for the Mn-based sample 2 (Tc = 23.8 K). The magnetic entropy change ΔS due to applied field change ΔH as a function of temperature was determined by the magnetization and heat capacity measurements. The maximum value of ΔS at μ0ΔH = 5 T is 6.1 J mol−1 K−1 (5.9 J kg−1 K−1) for 1 at T = 14 K and 6.7 J mol−1 K−1 (6.5 J kg−1 K−1) for 2 at T = 25 K. MCE data at different applied fields have been presented as one universal curve, which confirms magnetic transitions in 1 and 2 to be of second order. The temperature dependences of the n exponent characterizing the dependence of ΔS on ΔH have been obtained. The n(Tc) values, consistent with the shape of the magnetization curves, pointed to the 3D Heisenberg behaviour for 2 and some anisotropy, probably of the XY type, for 1. The (H/Tc)2/3 dependence of the maximum entropy change has been tested in the ferrimagnetic Mn2–L–[Nb(CN)8] (L = C3H4N2, C4H4N2) series.
departmental parameterization:	30
affiliation:	Wydział Chemii : Zakład Chemii Nieorganicznej
type:	journal article
subtype:	academic paper