Magnetocaloric effect in Mn2-pyrazole-[Nb(CN)8] molecular magnet by relaxation calorimetry.

Magnetocaloric effect in {[Mn(pyrazole) 4 ] 2 [Nb(CN) 8 ]·4 H 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 N ≈ 22.8 K . Temperature dependences of the magnetic entropy change Δ S M as well as the adiabatic temperature change Δ T ad due to applied field change μ 0 Δ H in the range of 0.1–9 T have been inferred from the relaxation calorimetry measurements. A systematic approximate approach has been used to determine the lattice contribution to the heat capacity. The maximum value of Δ S M for μ 0 Δ H = 5 T is 6.83 J mol −1 K −1 (6.65 J kg −1 K −1 ) at 24.3 K. The corresponding maximum value of Δ T ad is 1.4 K at 23.8 K. The temperature dependence of the exponent n characterizing the field dependence of Δ S M has been estimated. It attains the value of 0.64 at the transition temperature, which is consistent with the 3D Heisenberg universality class. A hitherto unobserved two-peak structure has been revealed in the temperature dependence of Δ T ad . [ABSTRACT FROM AUTHOR]