The study of entropy change and magnetocaloric response in magnetic nanoparticles via heat capacity measurements

In our work, we have investigated the magnetocaloric effect (MCE) of core@shell Co@Au nanoparticles by heat capacity Cp measurement in temperature range 1.9-55 K under external magnetic field. After the subtraction of lattice heat capacity contribution, the maximum of isothermal magnetic entropy change ΔSm= 3.11 J K−1 kg−1 was obtained at field change from 0 to 9 T. Adiabatic temperature change ΔTad= 3.31 K, refrigerant capacity power RCP = 88.9 J kg−1 and efficiency of adiabatic temperature change η = 0.37 K/T at the same external magnetic field change were established for the investigated system. The comparison of the results to the independent magnetic measurements data revealed the accordance of fundamental magnetocaloric characteristics obtained by both methods. Thus, this work is also the first experimental confirmation of relation between magnetocaloric response of nanoparticles and the low temperature magnetic transition from superparamagnetic to blocking/freezing state.