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arXiv · 1312.0744

Magnetocaloric effect in {[Fe(pyrazole)$_4$]$_2$[Nb(CN)$_8$]$\cdot$4H$_2$O}$_n$ molecular magnet

R. Pelka·P. Konieczny·P. M. Zielinski·T. Wasiutynski·Y. Miyazaki·A. Inaba·D. Pinkowicz·B. Sieklucka
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Abstract

Magnetocaloric effect in {[Fe(pyrazole)$_4$]$_2$[Nb(CN)$_8$]$\cdot$4H$_2$O}$_n$ molecular magnet is reported. It crystallizes in tetragonal I4$_1$/a space group. The compound exhibits a phase transition to a long range magnetically ordered state at $T_\mathrm{c}\approx$8.3 K. The magnetic entropy change $\Delta S_\mathrm{M}$ as well as the adiabatic temperature change $\Delta T_\mathrm{ad}$ due to applied field change $\mu_0\Delta H$=0.1, 0.2, 0.5, 1, 2, 5, 9 T as a function of temperature have been determined by the relaxation calorimetry measurements. The maximum value of $\Delta S_\mathrm{M}$ for $\mu_0\Delta H=5$ T is 4.9 J mol$^{-1}$ K$^{-1}$ (4.8 J kg$^{-1}$ K$^{-1}$) at 10.3 K. The corresponding maximum value of $\Delta T_\mathrm{ad}$ is 2.0 K at 8.9 K. The temperature dependence of the exponent $n$ characterizing the field dependence of $\Delta S_\mathrm{M}$ has been estimated. It attains the value of 0.64 at the transition temperature, which is consistent with the 3D Heisenberg universality class.

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R. Pelka, P. Konieczny, P. M. Zielinski, T. Wasiutynski, Y. Miyazaki, A. Inaba, D. Pinkowicz, B. Sieklucka. 2013-12-03. Magnetocaloric effect in {[Fe(pyrazole)$_4$]$_2$[Nb(CN)$_8$]$\cdot$4H$_2$O}$_n$ molecular magnet. https://doi.org/10.1016/j.jmmm.2013.11.047

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