Low-lying magnetic excitations and magnetocaloric effect of molecular magnet K6[V15As6O42(H2O)] • 8H2O

Low-temperature heat capacity measurements were performed on the molecular nanomagnet K-6[V15As6O42(H2O)] center dot 8H(2)O (V15). The low-lying magnetic excitations are clearly evidenced by the Schottky anomalies in the specific-heat data. The energy levels determined from the low-temperature observables agree well with the three-spin model for V15. The magnetocaloric effect of V15 is examined. The maximum entropy change of 5.31 Jkg(-1)K(-1) is found for a field change of Delta H = (8 - 0.5) T at similar to 1.5 K. In spite of the low ground-state spin of V15, a drastic entropy change of 4.12 Jkg(-1)K(-1) is observed for a field change of Delta H = (8 - 0.05) T at 0.4 K, which is comparable to the entropy change of some high-spin sub-kelvin magnetic coolers at such low temperatures. Anisotropy and consequent zero-field splitting result in this characteristic of V15 and may open new possibilities in the design of ultra-low-temperature molecular coolers. Copyright (C) EPLA, 2015