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

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 $\mathrm{\Delta }{S}_{\mathrm{M}}$ as well as the adiabatic temperature change $\mathrm{\Delta }{T}_{\mathrm{a}\mathrm{d}}$ due to applied field change ${\mu }_0\mathrm{\Delta }H$=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 $\mathrm{\Delta }{S}_{\mathrm{M}}$ for ${\mu }_0\mathrm{\Delta }H=5$ 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 $\mathrm{\Delta }{T}_{\mathrm{a}\mathrm{d}}$ 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.