This work focuses on fabricating a photocatalyst nanocomposite based on MnFe₂O₄@ZnO for degrading Red Amaranth azo dye. Manganese ferrite (MnFe₂O₄) magnetic nanoparticles were synthesized via a hydrothermal method, while a ZnO thin film, acting as the photoactive layer, was deposited on the magnetic cores using the atomic layer deposition (ALD) technique. X-ray diffraction (XRD) confirmed the spinel ferrite structure of MnFe₂O₄ and the hexagonal wurtzite phase of ZnO. The crystallite size, determined from the (311) peak, was 36.5 nm; this value was consistent with the average size of 33.2 nm measured by transmission electron microscopy (TEM). Magnetic characterization via vibrating sample magnetometry (VSM) at room temperature revealed a superparamagnetic behavior, determined by a very small hysteresis loop. The ZnO coating, achieved with 200 ALD cycles, resulted in a degradation efficiency η_eff of approximately 60% for the Red Amaranth dye. Finite-difference time-domain (FDTD) simulations provided theoretical insights into the electromagnetic interactions driving the photodegradation process, supporting the UV-vis absorbance data of the AZO dye. This nanocomposite can be considered as a soft magnetic material that offers promising applications in nanotechnology for environmentally friendly wastewater treatment and remediation.

To determine the gas temperature of an alternating current (ac) (50 kHz) arc discharge at atmospheric pressure in air, a Mach–Zehnder type interferometer was built, utilizing an He-Ne $(lambda=6328 hboxAA)$ laser source with vertical polarization and a power of 5 mW. Upon introducing the arc discharge into one of the interferometer arms, a displacement of interference fringes takes place with respect to its position without the discharge. Keeping in mind that displacement of the fringes is related to the difference of the optical path with the variation of the refraction index and with temperature change in the discharge zone; the latter was determined from the displacements of the interference fringes. At the center of the discharge channel, a temperature near 3000 K was calculated, diminishing gradually to room temperature toward the discharge borders. This temperature value at the center of the channel agrees with results previously reported in similar discharges. This is an alternate method for the diagnosis of plasma parameters used in the production and treatment of materials.