Structural characterization and magnetic properties of sol–gel derived ZnxFe3–xO4 nanoparticles

• A modified inorganic sol–gel method was applied to prepare ZnxFe3–xO4 nanoparticles.
• Nanoparticles exhibit narrow size distribution with a particle size of 5–10 nm.
• The compositions with a higher magnetization value than magnetite were obtained.
• The synthesized ZnxFe3–xO4 nanoparticles with x=0, 0.18, 0.45, 1 are superparamagnetic at room temperature.

Nanocrystalline ZnxFe3–xO4 solid solutions (with x=0, 0.18, 0.45, 1) with crystallite sizes of 5–10 nm, specific surface of about 180 m2/g were synthesized via an inorganic variant of the sol–gel approach. The composition and structure of the formed nanoparticles were examined with the help of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma atomic emission spectrometry and Fourier transform infrared spectroscopy. Hysteresis loops recorded for the samples indicate their ferromagnetic behavior at 5 K and superparamagnetic behavior at 300 K. The highest maximum magnetization of 59 emu/g at room temperature corresponds to Zn0.18Fe2.82O4 composition, and at 5 K to Zn0.45Fe2.55O4 (86 emu/g). The saturation magnetization of the pure magnetite was measured to be respectively 62 and 49 emu/g.