Colossal permittivity, resistive and magnetic properties of zinc substituted manganese ferrites

Abstract

Zinc substituted manganese ferrites, i.e., Mn1−xZnxFe2O4 (0.0 ≤ x ≤ 1.0) were synthesized by the citrate sol-gel route. Rietveld refinement of the X-ray diffraction patterns revealed the development of a single-phase cubic spinel structure with space group Fd3̅m. The stoichiometry of the prepared samples was confirmed by energy dispersive X-ray spectroscopy. The 57Fe Mössbauer study suggested the presence of Fe3+ and Fe2.5+ (mixed Fe3+ and Fe2+) ions at the tetrahedral and octahedral sites of the mixed spinel structure, respectively. However, the fraction of Fe2+/Fe3+ ions present at the octahedral site strongly depends on the site preference of Mn2+ and Zn2+ ions for both sites. Thus, the cation distribution among the tetrahedral and octahedral sites altered with increasing Zn2+ substitution (x). Impedance spectroscopy analysis displayed an enhancement in the resistive properties of MnFe2O4 with Zn2+ substitution, while the dielectric permittivity of the prepared samples exhibited a colossal value of the order of 104–107 at room temperature. This enhancement in the resistive and dielectric properties can be understood in terms of particle size, cation distributions, and conductivity inhomogeneity at the grain boundaries. The temperature-dependent ac conductivity analysis proposed that the short-range hopping of oxygen vacancies is responsible for the conduction process in the prepared samples. Here, our findings of high resistance (107), colossal permittivity (106), diminished tangent loss (0.018), and high magnetization (48 emu/g) for the Mn0.4Zn0.6Fe2O4 make this composition promising for radar absorbing applications.