Understanding the structural, magnetic, and electrical properties of MFe2O4 (M = Mg2+, Co2+, Ni2+, Cu2+, Zn2+) nanocrystalline ferrites. A comparative study

The present study aimed to understand the structural, magnetic, and electrical features of MFe₂O₄ nanocrystals (M = Mg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) synthesized via simple co-precipitation route and doing a comparative study with materials prepared using other routes. XRD showed the single-phase cubic structure formation for the samples only after calcination at 700^oC. An exception was obtained with MgFe₂O_4, which retains the Fe₂O₃ secondary phase, and CuFe₂O_4, which showed a structure transformation into a tetragonal phase. FT-IR spectroscopy indicated the pronouncing of the atomic weight effect on the ionic radii when discussing the present difference in the bands` positions. Agglomerated sphere-like cluster morphologies were detected through a TEM study. Magnetic studies showed ferromagnetic properties for CoFe₂O₄ and CuFe₂O₄, as well as superparamagnetic properties for the other ferrites. Also, only CoFe₂O₄ and CuFe₂O₄ showed hard ferrite types, while others indicated soft ones. The electrical investigations exhibited semi-conducting properties for all the samples, accompanied by a transition in the conduction mechanism from hopping to polaron as the temperature rose. The obtained conductivities order is CuFe₂O₄ > CoFe₂O₄ > ZnFe₂O₄ > NiFe₂O₄ > MgFe₂O₄. The low dielectric values obtained suggest the use of entire ferrites in microwave applications.