Structural, Electrical, and Magnetic Properties of Iron-Doped Zinc Oxide (Zn???Fe?O) Nanoparticles Synthesised via Co-precipitation Method

Transition metal-doped ZnO nanostructures are of considerable interest due to their multifunctionality in optoelectronics, spintronics, and magnetic applications. ZnO is a II–VI semiconductor with a direct band gap of 3.37?eV and high exciton binding energy, offering a suitable host lattice for transition metal doping [1–3]. Iron (Fe) is an attractive dopant because of its multiple oxidation states (Fe²?/Fe³?) that introduce defect-mediated magnetism in ZnO. The co-precipitation method is widely employed for its simplicity, low cost, and ability to produce homogeneous nanoparticles with controlled stoichiometry [4–6]. Fe doping can modify ZnO’s crystal structure, magnetic ordering, and electrical properties, making it promising for dilute magnetic semiconductors (DMSs) and multifunctional devices [7–9]. This study investigates 0.05?M Fe-doped ZnO nanoparticles synthesized via co-precipitation and calcined at 500?°C, focusing on structural, vibrational, magnetic, and electrical properties using XRD, FTIR, Raman, and VSM.

2. Experimental Methodology

MATERIALS

Zinc acetate dihydrate (Zn(CH?COO)?·2H?O), iron(III) chloride hexahydrate (FeCl?·6H?O), and sodium hydroxide (NaOH) were procured from Merck and used as received. Deionized water served as the solvent.

2.2 Synthesis Procedure

Stoichiometric amounts of zinc acetate and iron chloride corresponding to 0.05?M Fe doping were dissolved in deionized water under continuous stirring. NaOH solution was added dropwise to maintain a basic environment and form a homogeneous precipitate. The precipitate was washed repeatedly with deionized water and ethanol, dried at 120?°C, and calcined at 500?°C for 3?h to improve crystallinity and remove residual organics.

2.3 Characterization Techniques

XRD: Cu Kα radiation (λ = 1.5406?Å) was used to examine crystal structure, phase purity, and lattice parameters.

FTIR: Spectra were collected in the 400–4000?cm?¹ range to detect metal–oxygen bonding and residual functional groups.

Raman Spectroscopy: Used to study lattice vibrations and confirm structural integrity.

VSM: Room-temperature magnetic hysteresis loops were measured to determine magnetic behavior.

Electrical Measurements: Two-probe method was employed on pressed pellets to measure resistivity.

RESULTS AND DISCUSSION

3.1 X-ray Diffraction (XRD)

XRD confirmed that Fe-doped ZnO nanoparticles crystallized in a single-phase wurtzite structure. No secondary peaks were observed, indicating successful Fe incorporation. Peak broadening suggested nanoscale crystallite size, estimated in the range of ~25–35?nm. Slight lattice distortion is attributed to substitution of Zn²? ions by Fe ions.

Figure 1: XRD pattern of 0.05?M Fe-doped ZnO nanoparticles calcined at 500?°C.

3.2 Fourier Transform Infrared Spectroscopy (FTIR)

FTIR spectra displayed characteristic Zn–O stretching vibrations, confirming metal–oxygen bonding. Weak bands corresponding to O–H stretching and bending were present due to adsorbed moisture. The absence of organic residue bands indicated effective calcination.

Figure 2: FTIR spectrum of 0.05?M Fe-doped ZnO nanoparticles.

3.3 Raman Spectroscopy

Raman spectra supported the XRD findings, confirming the wurtzite structure and lattice integrity. The spectral features indicated structural modifications due to Fe doping without the formation of secondary phases.

Figure 3: Raman spectrum of 0.05?M Fe-doped ZnO nanoparticles.

3.4 Magnetic Properties (VSM Analysis)

VSM measurements demonstrated weak ferromagnetic behavior at room temperature. The low saturation magnetization and remanence suggest dilute magnetic semiconductor characteristics, arising from Fe²?/Fe³? exchange interactions and oxygen vacancy-mediated spin coupling.

Figure 4: Room-temperature M–H hysteresis loop of 0.05?M Fe-doped ZnO nanoparticles.