Iron oxide-based magnetic nanoparticles for high temperature span magnetocaloric applications

The magnetocaloric effect of chemically synthesized Mn0.3Zn0.7Fe2O4 superparamagnetic nanoparticles with average crystallite size of 11 nm is reported. The magnitude of the magnetic entropy change (ΔS M), calculated from magnetization isotherms in the temperature range of 30 K to 400 K, increases from - 0.16 J-kg^-1K^-1 for a field of 1 T to - 0.88 J-kg^-1K^-1 for 5 T at room temperature. Our results indicate that ΔS M values are much higher than primarily reported values for this class of nanoparticles. ΔS M is not limited to the ferromagnetic-paramagnetic transition temperature; instead, it occurs over a broad range of temperatures, resulting in high relative cooling power.