Defect-Driven Magneto-Electrical and Impedance Characteristics of Rod-Like Zn-Substitution MnFe2O4 Nano-ferrite

Abstract Ferrite nanoparticles, particularly tunable mixed spinel ferrites (MFe ₂ O ₄ ), have multifunctional capabilities due to their A- and B-site cation distribution, allowing for applications in magnetic, electrical, catalytic, and biological technologies. In this work, we synthesized a rod-like zinc (Zn) -substitution nano manganese ferrite (Zn x Mn 1−x Fe ₂ O with x = 0.2) using a facile, economical, and environmentally benign sol–gel process. X-ray diffraction (XRD) patterns established formation of a face-centered cubic spinel structure with the (Fd3̅m) space group, with a secondary phase of α-Fe ₂ O ₃ . Field Emission Scanning Electron Microscope (FE-SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) confirm rod-like particles, while Raman spectra confirm the distinctive spinel modes (T 2g , E g , A 1g ) and Photoluminescence (PL) spectra indicate intense blue emissions due to oxygen-vacancy recombination and interstitial Zn defects. X-ray photoelectron spectroscopy (XPS) confirms presence of Zn ²⁺ , Mg ²⁺ , and Fe ²⁺ oxidation states. Zn 0.2 Mn 0.8 Fe ₂ O ₄ has soft-magnetic behavior with Ms = 53.21 emu/g, low coercivity (0.06 kOe), a squareness ratio of 0.10, and a magnetic moment of 2.19 µB, indicating normal nanoparticle-related magnetization decreases. Dielectric measurements demonstrate a frequency-dependent decline in permittivity (10 Hz – 2 MHz) due to interfacial polarization, while temperature-dependent studies (423–673 K) exhibit an increase in dielectric constant, associated with thermally activated dipolar alignment and relaxation behavior in dielectric loss. AC conductivity validates the ferrites' semiconducting character; however, impedance research shows that grain boundaries contribute more to overall resistance than grains. The results indicate that Zn 0.2 Mn 0.8 Fe ₂ O ₄ nanoferrites are a suitable candidate for high-frequency electronic device applications.