Speaker
Dr
Robert PEŁKA
(Institute of Nuclear Physics PAN, Kraków)
Description
Magnetocaloric effect for {[Mn(II)(pyrazole)4]2[Nb(IV)(CN)8]∙4H2O}n1), {Mn(II)2(imH)2(H2O)4[Nb(IV)(CN)8] ∙4H2O}n (2) and [Nb(IV){(μ-CN)4Mn(II)(H2O)2}2∙4H2O]n (3) is reported. The compounds belong to a class of 3D coordination polymers. They exhibit a phase transition to a long range magnetically ordered state at 22.8 K (1), 24.1 K (2), and 47 K (3). Heat capacity measurements by relaxation calorimetry in applied field of 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 7, and 9 T enabled to determine the magnetic entropy change ΔSM as well as the adiabatic temperature change ΔTad. The maximum values of ΔSM calculated for a field change of 5 T amount to 6.65 J kg-1 K-1 (1), 9.5 J kg-1 K-1 (2), and 9.01 J kg-1 K-1 (3). The corresponding maximum values of ΔTad are 1.4 K at 23.8 K (1), 2.02 K at 25.1 K (2), and 1.7 K at 49.0 K (3). The temperature dependence of the exponent n characterizing field dependence of ΔSM has been estimated. Exponent n attains the value of 0.64 (1), 0.67 (2), and 0.69 (3) at the transition temperature, which is close to that expected for the three-dimensional Heisenberg universality class. Universal scaling of the magnetic entropy change is discussed.
Primary author
Dr
Robert PEŁKA
(Institute of Nuclear Physics PAN, Kraków)
Co-authors
Prof.
Barbara Sieklucka
(Faculty of Chemistry, Jagiellonian University, Kraków)
Dr
Dawid Pinkowicz
(Faculty of Chemistry, Jagiellonian University, Kraków)
Mr
Marcin Gajewski
(Institute of Nuclear Physics PAN, Kraków)
Mr
Piotr Konieczny
(Institute of Nuclear Physics PAN, Kraków)
Prof.
Tadeusz Wasiutyński
(Institute of Nuclear Physics PAN, Kraków)
Prof.
Yasuhiro Nakazawa
(Department of Chemistry, Graduate School of Science, Osaka University)
Prof.
Yuji Miyazaki
(Research Center for Structural Thermodynamics, Graduate School of Science, Osaka University)
