Structural, magnetic and photoluminescence properties of Zn-Ni ferrites synthesized by hydrothermal method

•ZnxNi1-xFe2O4 (0 ≤ x ≤ 1.0) nanoferrites synthesized by hydrothermal method.•XRD confirmed the formation single-phase spinel structure.•Magnetization measurements revealed the paramagnetic nature of the nanoparticles.•Photoluminescence revealed blue-violet emission.•Defects can make ZnxNi1-xFe2O4 ferrites beneficial to gas sensing applications. Nanocrystalline ZnxNi1-xFe2O4 (0 ≤ x ≤ 1.0) ferrites were synthesized by hydrothermal method. XRD analysis showed that all compositions crystallize with a cubic spinel-type structure with an average crystallite size in the range of 17–27 nm which corresponded to particle sizes obtained from TEM. The lattice parameter increased from 8.289 to 8.432 Å with increasing Zn content. The ZnxNi1-xFe2O4 nanoferrites exhibit superparamagnetic behaviour at room temperature (RT). The saturation magnetization (Ms) varies considerably with Zn content to reach a maximum value for Zn0.5Ni0.25Fe2O4 composition, i.e. 41.893 emu/g. The high Ms and magnetic moment values are attributed to cation distribution change. The electron spin resonance (ESR) results demonstrated g-values ranging between 2.005 and 2.621 which indicated strong exchange interaction between nanoparticles, type of morphology, and crystalline nature of particles. These low g-values make ZnxCo1-xFe2O4 nanoferrites suitable for applications in low-frequency devices. The Mössbauer spectroscopy results revealed the transition from ferromagnetic to paramagnetic state, by showing collapse of sestet to quadrupole doublet. The optical properties of the nanoferrites were investigated photoluminescence (PL) spectra. The broad visible emission band at 427 nm (2.90 eV), 471 nm (2.60 eV) and 520 nm (2.38 eV) were observed in all PL spectra. The electron spin resonance and photoluminescence results show that Zn-Ni ferrites are good candidates for blue LEDs and in gas sensing applications.