Synthesis and electromagnetic properties of porous MnFeCoO4 structures by a facile sol-gel auto combustion method

We report the correlation between the microstructure, magnetic, and high-frequency electromagnetic properties of porous MnFeCoO4 structures synthesized by the simple sol-gel auto combustion method. The as-prepared (AP) samples were annealed in the temperature range of 350-1200 degrees C in air to perceive the temperature's influence on the morphology and properties. The field emission scanning electron microscopy (FESEM) analysis revealed the porous structures with the pore size varies from 100 to 350 nm. The number of pores decreased significantly with the increase of annealing temperature due to the rise of pore and particle size of the agglomerated nanoparticles. Interestingly, the annealing temperature leads to the development of hexagonal planes extended on the particles' surfaces. The X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) studies confirm the cubic spinel phase formation. The magnetization (coercivity) of the AP NPs is 27.9 emu/g (632 Oe), which increases (decreases) with the rise of annealing temperature and finally reached a value of 50.6 emu/g (39.5 Oe) for the sample annealed at 1200 degrees C. Moreover, the dielectric loss of AP sample is enhanced compared to the annealed samples, which originates from the porous structure, large surface area, and dipole/interfacial polarization.