The magnetocaloric effect of chemically synthesized Mn_(0.3)Zn_(0.7)Fe_2O_4 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~(-1)K~(-1) for a field of 1 T to -0.88 J-kg~(-1)K~(-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.
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