Correlation of dielectric, electrical and magnetic properties near the magnetic phase transition temperature of cobalt zinc ferrite

Multiferroic composite structures, i.e., composites of magnetostrictive and piezoelectric materials can be envisioned towards the goal of achieving strong room-temperature ME coupling for real practical device applications. Magnetic materials with high magnetostriction, high Néel temperature (T_N), high resistivity and large magnetization are required to observe high ME coupling in composite structures. In continuation to our investigations for suitable magnetic candidate for multiferroic composite structures, we have studied the crystal structure, dielectric, transport, and magnetic properties of Co_0.65Zn_0.35Fe₂O₄ (CZFO). Rietveld refinement of X-ray diffraction patterns confirms the phase purity with cubic crystal structure with (Fd3m) space group; however, we have found a surprisingly large magnto-dielectric anomaly at the Neel temperature, unexpected for a cubic structure. The presence of mixed valences of Fe⁺²/Fe⁺³ cations is probed by X-ray photon spectroscopy (XPS), which support the catonic ordering-mediated large dielectric response. Large dielectric permittivity dispersion with a broad anomaly is observed in the vicinity of the magnetic phase transition temperature (T_N) of CZFO suggest the strong correlation between dielectric and magnetic properties. The ferromagnetic-paramagnetic phase transition of CZFO has been found ~640 K, which is well above room temperature. CZFO exhibits low loss tangent, high dielectric constant and large magnetization with soft magnetic behavior above room temperature. We describe the possible potential candidates for multiferroic composite structures as well as for multifunctional and spintronics device applications.