Magnetic and thermal modulation of DC-AC electrical properties in Zn0.3Ni0.7Fe2O4 nanoparticles

Abstract

In the pursuit of efficient magnetic nanoparticles for device applications, Zn_0.3Ni_0.7Fe₂O₄ nanoparticles were synthesized via a low-temperature pyrophoric reaction to explore their DC and AC electrical properties under varying magnetic fields and temperatures. Structural analysis using X-ray diffraction confirmed a single-phase spinel structure with an average crystallite size of ∼38 nm, while FE-SEM revealed a homogeneous surface morphology. EDX confirmed the elemental composition without impurities. DC electrical studies showed a ∼330 % enhancement in current at 20 V and 2.0 kOe, attributed to oxygen vacancies and improved charge carrier mobility. The current–voltage behavior exhibited finite short-circuit current and open-circuit voltage, indicating charge storage via interfacial polarization at grain boundaries. AC measurements revealed a high dielectric constant at low frequencies, governed by interfacial polarization, with a magnetodielectric effect of ∼14 % and a magnetoimpedance change of ∼−10.7 % at 2.0 kOe (200 Hz). Impedance spectroscopy and Nyquist plot modeling showed that grain and grain boundary contributions dominate the conduction process. Magnetic field application reduced resistance and increased capacitance, suggesting field-assisted conduction. Temperature-dependent studies indicated a transition from metallic to semiconducting behavior, supported by analysis of the real and imaginary parts of impedance. AC conductivity followed Jonscher’s power law, with small polaron hopping dominating at lower temperatures and large polaron hopping becoming significant beyond the transition, indicating thermally activated conduction. These results demonstrate the strong magnetoelectric coupling and conduction tunability of Zn_0.3Ni_0.7Fe₂O₄ nanoparticles, making them promising candidates for multifunctional device applications.