Abstract
We calculated the magnetocaloric properties of the molecular nanomagnet Cu5-NIPA, consisting of five spins arranged in two corner-sharing triangles (hourglass-like structure without magnetic frustration). The thermodynamics of the system in question was described using the quantum Heisenberg model solved within the field ensemble (canonical ensemble) using exact numerical diagonalization. The dependence of the magnetic entropy and magnetic specific heat on the temperature and the external magnetic field was investigated. The isothermal entropy change for a wide range of initial and final magnetic fields was discussed. Due to plateau-like behavior of the isothermal entropy change as a function of the temperature, a high degree of tunability of magnetocaloric effect with the initial and final magnetic field was demonstrated.
Highlights
Molecular magnets constitute a highly interesting class of modern magnetic materials [1,2], the rapid development of which over the last decades [3,4,5,6,7] required concerted effort of theoreticians and experimentalists
magnetocaloric effect (MCE) [16] consists in the dependence of the entropy of substance on the external magnetic field and allows designing of a thermodynamic cycle for refrigeration or outlining the procedure used to lower the temperature [17]
The interest is focused on the magnetocaloric properties, such as magnetic entropy, magnetic specific heat, and isothermal entropy change, which are expressed per mole of the substance of interest
Summary
Molecular magnets constitute a highly interesting class of modern magnetic materials [1,2], the rapid development of which over the last decades [3,4,5,6,7] required concerted effort of theoreticians and experimentalists. The constant quest for optimized materials for exploiting MCE motivates studies of novel relevant materials [18] This focuses the attention on molecular magnets as highly promising materials. In the context of the theoretical modeling of magnetic entropy and magnetocaloric properties of zero-dimensional systems, numerous works concerning spin clusters of various geometry can be mentioned first, especially those for spins 1/2. The calculations become more even more demanding when structures involving high number of spins, especially S > 1/2, are modeled For this purpose, advanced and effective close-toexact approaches for thermodynamic description of the spin systems are developed [52,53,54,55]. The theoretical model used to describe the MCE in Cu5-NIPA is outlined, the numerical results for the thermodynamic quantities of interest are discussed, and conclusions are drawn
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