Effect of Ni substitution and annealing temperature on structural and magnetic properties of MnZn-Ferrites: Cytotoxicity study of ZnO and SiO2 coated core shell structures

[Display omitted] •Impurity formation suppressed at optimal composition for Mn0.2Zn0.4Ni0.4Fe2O4.•Improved magnetic behavior in Ni-MZFs annealed at moderate temperatures.•Ni-MZFs enhanced magnetization (65–73 emu/g) compared with MZF (35 emu/g).•Coating (ZnO and SiO2) Ni-MZFs yielded stable spinel structure and magnetization.•Ni-MZF NPs and core shell structures had soft magnetization and biocompatibility. Magnetic spinel ferrite nanoparticles (NPs) have a broad scope of applications based on their structural properties, including in lithium-ion batteries, catalysts, electrochemical energy storage, drug delivery, magnetic hyperthermia, and photothermia. In this study, we investigated the structure, crystallographic phase formations, and magnetic properties of Ni-substituted MnZn ferrites (MZFs), Mn(0.6-x)Zn(0.4-y)Ni(x+y)Fe2O4 (x = 0–0.6, y = 0; y = 0–0.4, x = 0) compositions of as-prepared (AP) and air annealed (350–1200 °C) samples. All AP NPs exhibited a pure spinel structure. Ni-MZF compositions annealed at 600 °C had high α-Fe2O3 secondary phase content in Ni-MZFs (Ni substituted for Zn), whereas Ni-MZFs with x = 0.4 (Ni substituted for Mn) had no impurities, and its magnetization (50 emu/g) was enhanced compared with that of the other samples. X-ray photoelectron spectroscopy revealed that Fe3+ cations were present in tetrahedral and octahedral sites. The single spinel phase reappeared with improved crystallinity in all Ni-MZFs by annealing at 1200 °C and exhibited superior magnetization (60–73 emu/g) compared with that of MZF (35 emu/g). Additionally, the spinel phase was stabilized in the ZnO- and SiO2-coated Ni-MZF core shell structures annealed at 700 °C with higher magnetization than MZF. Moreover, Ni-MZF core shell structures exhibited biocompatibility and may have biomedical applications.