Chavez-Baldovino, Ermides

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    Magnetic and structural characterization of solid solution NixZn(1-x)Fe2O4 (x = 0.5 AND x = 1) synthesized by high energy ball milling
    (2013) Chavez-Baldovino, Ermides; Uwakweh, Oswald; College of Arts and Science - Science; Castellanos, Dorial; Radovan, Henri A.; Department of Physics; Colón, Omar
    Mechanochemical reactions of NiO, ZnO, and α-Fe2O3 were carried out in a planetary mill to produce Nickel ferrite (NiFe2O4) and Nickel-Zinc ferrite (Ni0.5Zn0.5Fe2O4) nanocrystallites. All measurements were made at room temperature under identical processing conditions entailing initial addition of 0.6 mL of acetone as surfactant with hardened stainless steel grinding materials. The average crystallite sizes of the particles as determined from X-ray diffraction measurements decreased as a function of milling time, with values between 7.38 and 5.35 nm. Specific Saturation Magnetization determined from Vibrating Sample Magnetometer measurements varied with the milling time and reached a maximum value of 61.94 Am2/Kg (61.94 emu/g). From 1 mT, the coercivity displayed tendency to increase with increasing milling time for the end-member Nickel ferrite phase (NiFe2O4) for the three ball to powder ratios (BPR) used. Similar behavior was observed for the x = 0.50 composition (Ni0.5Zn0.5 Fe2O4) ferrite. Room temperature Mössbauer spectra of all samples exhibited non-magnetic peaks, which evolved from the sextets associated with the precursor hematite phase, and ultimately a total collapse of the sextets due to the relaxation effects linked to the superparamagnetic effect. The rate of the mechanochemical synthesis process depended on the BPR used. The time to achieve NiFe2O4 phase was shorter for a BPR of 40:1, when compared to the BPR of 20:01 and 10:01, cases respectively. The superparamagnetic behavior was observed for all ball milled compositions, for crystal sizes less than 7.38 nm.