Magnetic and optical properties of synthesized ZnO-ZnFe2O4 nanocomposites via calcined Zn-Fe layered double hydroxide

In this article, Zn-Fe layered double hydroxide (Zn-Fe-CO3-LDH) precursors with 1, 2, 3, and 4 values of Zn2+/Fe3+ molar ratio were prepared by coprecipitation method at pH = 8. ZnO/ZnFe2O4 nanocomposite was obtained as the calcination process of LDH precursors. Herein, we explore a prospective strategy to synthesize the zinc ferrite nanostructure by the calcination of Zn-Fe-CO3-LDH precursors. Powder X-ray diffraction (PXRD) exhibited two phases (ZnO and ZnFe2O4). Hall method has been used to calculate the grain size of ZnFe2O4 and was obtained between 19 nm and 32 nm. Magnetic measurements of the ZnFe2O4 phase after the subtraction of the paramagnetic contribution from the whole hysteresis loop of ZnO/ZnFe2O4 nanocomposite were investigated using VSM. The high coercivity values of ZnFe2O4 nanoparticles (similar to 2600 Oe) and low values of the anisotropy constant (0.0004-0.0796) J/m(3) were observed which were useful for high-density storage devices application. The values of the optical band gap of the ZnFe2O4 phase were obtained above the bulk value (2.18-2.33 eV) due to the nanosized ZnFe2O4 nature. The Urbach tail energy of ZnFe2O4 nanoparticles was found between 160.3 and 194.1 meV which indicated high localized defect levels in the forbidden band gap of prepared samples. The refractive index relation with photon energy showed normal dispersion behavior for samples at the range below 1.8 eV and anomalous dispersion behavior at the range above 1.8 eV. The values of normal dispersion parameters were calculated in this work for ZnFe2O4 nanostructure as new results which were candidate material in tele-communication applications. All these parameters, in general, increased with the increasing of the Zn2+/Fe3+ molar ratio.