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The multiferroic (Bi_0.95RE_0.05)(Fe_0.95Mn_0.05)O₃ (where RE = Pr, Tb and Dy) has been synthesized using solid-state reaction technique. Effects of Pr, Tb and Dy substitution on the structure, electrical and ferroelectric properties of (Bi_0.95RE_0.05)(Fe_0.95Mn_0.05)O₃ samples have been studied by performing X-ray diffraction, dielectric measurements and magnetic measurements. The crystal structure of the ceramic samples have a monoclinic phase. The vibrating sample magnetometer (VSM) measurement shows a significant change in the magnetic properties of Pr-, Tb- and Dy-doped (Bi_0.95RE_0.05)(Fe_0.95Mn_0.05)O₃. It is seen that coercive field (H_c) and remanent magnetization (M_r) increases for Pr but decreases for Dy and Tb.

The compositional dependence of ac conductivity (${\sigma }_{\mathrm{\text{ac}}}$), real ($\sigma$′) and imaginary ($\sigma$′′) parts of complex electric conductivity ($\sigma$*) was investigated as a function of temperature ($T$) and frequency ($f)$ for Mn${}_{0.7{+x}_{}}$Zn${}_{0.3}$Si_xFe${}_{2–{2x}_{}}$O₄, $x=0.0$, 0.1, 0.2 and 0.3 spinel ferrite system. The compositional dependence of lattice constant values suggested that the most of the substituted Si${}^{4+}$-ions reside at grain boundaries and only a few Si-ions are inside grains. The variation of ${\sigma }_{\mathrm{\text{ac}}}(x$, $f$, $T)$ is explained on the basis of segregation and diffusion of Si${}^{4+}$ ions at grain boundaries and grains, respectively, and the electrode effect. Thermal variation of ac conductivity at fixed frequency suggested two different mechanisms which could be responsible for conduction in the system. It is found that $\sigma$* is not the preferred presentation for dielectric data and the scaling process of real part of conductivity by normalized frequency and the scaled frequency were found unsuccessful. The fitting results of ac conductivity data with path percolation approximation were found suitable in low-frequency regime while in high-frequency regime, effective medium approximation (EMA) was found successful.

Spinel ferrite ${\text{Ni}}_{0.08}$${\text{Mn}}_{0.90}$${\text{Zn}}_{0.02}$Fe₂O₄ was prepared by a conventional ceramic process followed by sintering at three different temperatures (1050${}^{\circ }$ C, 1100${}^{\circ }$ C and 1150${}^{\circ }$ C). X-ray diffraction (XRD) investigations stated the single-phase cubic spinel structure and the FTIR spectra revealed two prominent bands within the wavenumber region from 600 cm${}^{-1}$ to 400 cm${}^{-1}$. Surface morphology showed highly crystalline grain development with sizes ranging from 0.27 $\mu$m to 0.88 $\mu$m. The magnetic hysteresis curve at ambient temperature revealed a significant effect of sintering temperature on both coercivity ($H_c)$ and saturation magnetization ($M_s)$. Temperature caused a decrease in DC electrical resistivity, while the electron transport increased, suggesting the semiconducting nature of all samples and that they well followed the Arrhenius law from which their activation energies were determined. The values of Curie temperature ($T_c)$ and activation energy were influenced by the sintering temperature. Frequency-dependent dielectric behavior (100 Hz–1 MHz) was also analyzed, which may be interpreted by the Maxwell–Wagner-type polarization. The UV–vis–NIR reflectance curve was analyzed to calculate the bandgap of ferrites, which showed a decreasing trend with increasing sintering temperature.

Single phase nanocrystalline soft magnetic Mg_0.7-xNi_0.3Zn_xFe₂O₄, ferrites with x = 0.0 − 0.7 were prepared by sol gel auto-combustion method. X-ray diffraction confirms the formation of single phase nano-crystalline cubic spinel ferrites with average grain diameter ranging between 12.9 nm to 23.9 nm. Formation of the ferrite phase without subsequent heat treatment makes sol-gel auto combustion technique especially suitable and economical for the large scale industrial production of the nano-crystalline ferrites for multilayer chip inductor applications (MLCI). Both, lattice parameter and X-ray density shows a linear increase with increasing Zn²⁺ concentration, attributed to the difference in ionic radii and density of Mg and Zn. Increase in Zn content enhances the soft magnetic behavior, exhibiting linear decrease of coercivity from 122.34 Oe to 72.45 Oe, explained by increase of density with Zn addition. The maximum magnetization (M_max)increases up to 0.106 Tesla (for x = 0.4) and. then decreases with increase of Zn content, discussed on the basis of increase of the occupancy of A-site in spinel ferrite by non-magnetic Zn²⁺ ion.