Magnetocaloric effect of high-spin cluster with Ni9W6 core

• Magneto-thermal properties of a unique cluster compound are studied.
• Magnetocaloric effect is derived from calorimetric experiments.
• Systematic scheme of extracting MCE from calorimetric data is developed.

A study of magnetocaloric effect of a structurally unique molecular magnet built of spin clusters with the pentadecanuclear Ni(II)9W(V)6 core forming a cube-like framework is reported. The compound crystallizes in the triclinic system. The clusters display anisotropy quantified with the axial D=0.07 K and rhombic E=0.023 K anisotropy constants. The temperature dependences of magnetic entropy change ΔSM as well as the adiabatic temperature change ΔTad due to applied field change μ0ΔH ranging from 1 to 9 T have been determined by employing the relaxation calorimetry measurements in applied field. The maximum value of ΔSM for μ0ΔH=5 T is 18.38 J K−1 mol−1 (3.36 J K−1 kg−1) at 4.3 K. The corresponding maximum value of ΔTad=4.6 K is attained at 2.2 K. The occurrence of the inverse MCE has been observed at high temperatures for small field change values. The temperature dependence of the exponent n characterizing the field dependence of ΔSM has been estimated and discussed. The study revealed that the compound may be treated as a possible candidate for cryogenic magnetic cooling.