Composition- and Size-Controlled Synthesis of Mn-Zn Ferrite Nanocrystals for Potential Magnetocaloric Applications
E. Calderón-Ortiz, O. Perales-Perez, S. Urcio
University of Puerto Rico - Mayaguez, PR
Keywords: manganese-zinc ferrite nanocrystals, magnetocaloric application, rare earth dopants
Abstract:The use of ferromagnetic fluid for cooling applications where the fluid can be pumped with no moving mechanical parts, using the magnetocaloric effect, can be a great advantage for many applications where maintenance or power consumption are undesirable . A magnetic material suitable for this application has to fulfill certain requirements like tunable demagnetization temperature (Tc), high saturation magnetization (Ms) and high enough pyromagnetic coefficient. This work is focused on the synthesis of pure and Gd-doped MnxZn1-xFe2O4 nanoparticles as candidate materials for magnetocaloric pumping applications. The synthesis of the ferrite nanoparticles was carried out by a modified coprecipitation approach where the reactants were added at specific flow-rates . The maximum magnetization of Mn-Zn ferrite nanocrystals varied from 13emu/g to 59emu/g when ‘x’ was increased from 0.0 to 1.0, respectively. The demagnetization temperature for an external magnetic field of 2.2T, TC, ranged from 559K to 695K when ‘x’ was increased from 0.5 to 1.0, respectively. In turn, the maximum magnetization and TC of the Gd(0.01)-doped Mn(0.8)-Zn ferrite was 55emu/g and 604K, respectively. This TC value was below 675K, which corresponds to pure ferrite. The TC value for pure Mn(0.08)-Zn ferrite went down from 675K (no-control on flow-rate) to 591K (20 ml/min).