The nanosized structure and relative paramagnetic properties of ZnFe2O4 by the polyol processes and the heat treatment processes

The controlled synthesis and paramagnetic properties of nanosized Zn-Fe-O oxides have been researched by the polyol and the heat treatment processes designed according to drying, annealing, and sintering from low to high temperatures. The structural changes have led to change weak superparamagnetism of nanosized Zn-Fe-O oxides in the forms of hybrid nanosized ZnO/ZnFe₂O₄ oxides into paramagnetism of nanosized ZnFe₂O₄ when the as-prepared samples of both ZnO and ZnFe₂O₄ oxides were isothermally annealed and sintered from low temperature at about 60 °C to high temperature at 950 °C for 2 h during their structural phase transitions in all the measurements of x-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and SEM/energy dispersive X-ray spectroscopy (EDX) combined methods. Interestingly, it is experimentally confirmed that one original paramagnetic hysteresis consists of paramagnetic segments and closed curves. Both normal and abnormal paramagnetic properties of ZnFe₂O₄ were carefully investigated.