Synthesis and study on structural, magnetic, dielectric properties and impedance spectroscopy of nanosized Mn-doped γ-Fe₂O₃ for multifunctional applications

Nano structured samples of γ-Mn_xFe_2-xO₃ (0 ≤ x ≤ 1.0, step 0.2) were prepared by a wet-chemical method. The formation of the pure-phase FCC spinel structure of the samples has been confirmed by x-ray diffraction and Fourier Transform Infrared spectroscopy, where their crystallite size increases from 12 to 28 nm by adding Mn³⁺ ions. The high-resolution transmission electron microscopy images show spherical-shaped agglomerated nanoparticles with uniform size, confirming the nanostructure of the samples. The X-ray photoelectron spectroscopy and Mössbauer results confirm the existence of Fe³⁺ and Mn³⁺ ions and the disappearance of the Fe²⁺ and Mn²⁺ ions in the cubic structure of the γ-Mn_xFe_2-xO₃. The Brunauer–Emmett–Teller specific surface area of the samples ranges from 36 to 79 m²/g, where the sample of x = 0.2 has the largest value. The sigmoid-shaped hysteresis loops reflect the soft magnetic nature of the samples. As the Mn³⁺ ion addition increases, the M_s and M_r increase up to the sample of x = 0.4, then decrease again. The H_c, which has lower values, increases as the crystallite size increases, manifesting the single-domain nature of the particles and approaching the superparamagnetic limits. The composition dependence of σ_dc, σʹ_ac, εʹ, εʺ, and tanδ is dependent on grain size, specific surface area, and cation distribution.