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Nanostructure of Y-type hexaferrite with composition of Sr₂Ni₂Al_x/2Cr_x/2Fe_12-xO₂₂ (where x are 0, 0.6, 1.2, 1.8, 2.4 and 3) were prepared by sol–gel auto-combustion method. The influence of Al and Cr doping on the structural and magnetic properties has been investigated. The X-ray diffraction (XRD) patterns confirm phase formation of Y-type hexaferrite. The microstructure and morphology of prepared samples were studied by high resolution field emission scanning electron microscope (FESEM) which shows the hexagonal shape for all of the samples. Magnetic properties were characterized using vibrating sample magnetometer (VSM). The magnetic results revealed that by increasing the Al and Cr to the structure, the coercivity was also increased from 840 Oe to 1160 Oe. Moreover it has been shown that with addition of dopants, saturation magnetization (M_s) and remnant magnetization (M_r) were decreased from 39.61 emu/g to 30.11 emu/g and from 17.51 emu/g to 14.62 emu/g, respectively, due to the entrance of nonmagnetic ions into Fe³⁺ sites.

Doping of group-II divalent cations in LaMnO₃ can produce advanced multi-functionalities in these nano-manganite materials according to recent theoretical approaches. An experimental investigation of Mg, Sr and Ba-doped LaMnO₃ nano-structures has been made by synthesizing these compositions with fuel agent assistive sol–gel auto-combustion technique. Detailed structural studies were carried out for crystal structure, lattice parameters, crystallite size, density and strain in structure using the data obtained from X-ray diffraction (XRD). Structural parameters were largely affected and significantly varied in all compositions due to doping of group-II elements with different sized ionic radii. Morphological and compositional analyzes were carried out using scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Electrical and magnetic properties were explored using four-point probe and physical property measurement setups and observed a significant change in various compositions. The substitution of group-II atoms with different sized ionic radii on the regular sites in structure provides a distinctive behavior in various properties.

In this research, SrFe${}_{12-x}$Ni${}_x$O${}_{19}$ (x$=$ 0 − 1) hexagonal ferrites were prepared by sol-gel auto-combustion method. Effect of Ni substitution on structural, morphological and magnetic properties of nanoparticles was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. The XRD results confirmed that all samples with x$\le$ 0.5 have single phase M-type strontium ferrite structure, whereas for the SrFe${}_{12-x}$Ni${}_x$O${}_{19}$ samples with x$>$ 0.5, the spinel NiFe₂O₄ phase has also appeared. The lattice parameters and crystallite sizes of the powders were concluded from the XRD data and Williamson–Hall method. Magnetic analyses showed that the coercivity of powders decreased from 5672 Oe to 639 Oe while the saturation magnetization increased from 74 emu/g to 81 emu/g with nickel substitution. The results of this study suggest that the strontium hexaferrites doped with Ni are suitable for applications in high density magnetic recording media as well as microwave devices because of their promising magnetic properties.

Barium hexaferrite nanoparticles are attractive for modern data storage and microwave devices due to their unique properties. Single phase synthesis of barium hexaferrite using sol–gel auto-combustion route was optimized by varying sintering temperature and time. X-ray diffraction confirmed single phase hexagonal crystal structure of the sample sintered at 1100${}^{\circ }$C for 2 h. Crystallite size, as determined using Scherrer’s formula, was increased with the increase in sintering temperature while the porosity remained nearly unchanged. Field emission scanning electron microscope (FE-SEM) revealed that grain size was increased from nanometers to micrometers by rising the sintering temperature and the shape of particles was platelet-like hexagonal at 900${}^{\circ }$C. Vibrating sample magnetometer (VSM) exhibited that saturation magnetization and coercivity increased with the increase of sintering temperature. Maximum saturation magnetization and coercivity values were 36.80 emu/g and 5365 Oe, respectively, for the sample sintered at 1100${}^{\circ }$C for 2 h.

In this work, sol–gel auto-combustion technology is used to synthesize nanocrystalline Ni${}_{0.2}$Cu${}_{0.2}$Co${}_{0.6}$Fe₂O₄ with high purity metal nitrate and citric acid as precursor solution. The prepared samples are sintered at different temperatures (400${}^{\circ }$C, 500${}^{\circ }$C, 600${}^{\circ }$C, 700${}^{\circ }$C, 800${}^{\circ }$C, 900${}^{\circ }$C, 1000${}^{\circ }$C and 1100${}^{\circ }$C) for 3.5 h. The structure and magnetic properties of the samples are characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and vibrating sample magnetometer (VSM). The analysis of the XRD patterns confirms that all the samples have a single-phase cubic spinel structure. The particle size of the prepared samples (between 23 nm and 36 nm) is determined by the Scherrer equation. The effect of particle size is through observation of samples sintered at different temperatures. FT-IR spectroscopy shows the characteristic peak is near 588 cm${}^{-1}$. And the measurement also confirms the formation of spinel structure. The magnetic parameters of the samples are measured by VSM at room temperature with a maximum magnetic field of 1 T. Coercivity, remanent magnetization and saturation magnetization change with the changing sintering temperature. It can be clearly observed that the magnetic properties increase significantly with the temperature increasing from 600${}^{\circ }$C to 700${}^{\circ }$C. The dM/dH versus H curves are obtained by differentiating the hysteresis loop. The increasing peak height of dM/dH at $H_m$, indicates a magnetically stable state for the samples with good crystalline cubic spinel structure.

Manganese substituted nickel–copper–cobalt ferrite nanoparticles having the basic composition ${\mathrm{\text{Ni}}}_{0.2}{\mathrm{\text{Cu}}}_{0.2}{\mathrm{\text{Co}}}_{0.6-x}{\mathrm{\text{Mn}}}_x{\mathrm{\text{Fe}}}_2{\mathrm{\text{O}}}_4$ (x = 0.0, 0.1, 0.2, 0.3 and 0.4) were synthesized by sol–gel auto-combustion method. X-ray diffraction (XRD) was used to estimate phase purity and lattice symmetry. All the prepared samples show the single-phase cubic spinel structure. Fourier transform infrared (FTIR) measurements also confirm the cubic spinel structure of the ferrite that is formed. The preparation of samples show these nearly spherical particles by Transmission electron microscopy (TEM). The magnetic properties of Mn${}^{2+}$ ion substituted in nickel–copper–cobalt ferrite were studied by Vibrating sample magnetometer (VSM). The saturation magnetization ($M_s$), remanent magnetization $(M_r)$, coercivity $(H_c)$, magnetic moment $({\mu }_B)$ and anisotropy constant $(K)$ first increase and then decrease with the increase of ${\mathrm{\text{Mn}}}^{2+}$ ions content. They had better magnetism than pure sample and other substituted samples when the substitution amount of ${\mathrm{\text{Mn}}}^{2+}$ ions was $x=0.1$. At $x=0.1$, the maximum values of remanent magnetization $(M_r)$, saturation magnetization $(M_s)$ and coercivity $(H_c)$ are 25.58 emu/g, 61.95 emu/g and 689.76 Oe, respectively. This indicates that the magnetism of ferrite can improve by substituting with the appropriate amount of manganese. However, due to the excess ${\mathrm{\text{Mn}}}^{2+}$ ions instead, ferrite magnetism is weakened. This means that these materials can be used in magnetic data storage and recording media.

In order to study the effect of sintering temperature on the structure and magnetic properties of nickel-magnesium-cobalt ferrite, ${\mathrm{\text{Ni}}}_{0.2}{\mathrm{\text{Mg}}}_{0.2}{\mathrm{\text{Co}}}_{0.6}{\mathrm{\text{Fe}}}_2{\mathrm{\text{O}}}_4$ spinel ferrite with different sintering temperatures (500${}^{\circ }$C, 600${}^{\circ }$C, 700${}^{\circ }$C, 800${}^{\circ }$C, 900${}^{\circ }$C and 1000${}^{\circ }$C) was prepared by sol–gel method. The magnetic properties of the prepared samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Vibrating sample magnetometer (VSM). The results show that the sintering temperature has a significant effect on the structure and magnetic properties of nickel-magnesium-cobalt ferrite. Analysis of the XRD pattern confirmed that all samples showed a single-phase cubic spinel structure. The particle size of the prepared sample determined by the Scherrer equation was 51 nm to 135 nm. As the sintering temperature increases from 500${}^{\circ }$C to 1000${}^{\circ }$C, the intensity of all peaks gradually increases, the crystallinity and particle size of the sample increase significantly, but the coercive force decreases, the saturation magnetization, the residual magnetization and the squareness $(M_r/M_s)$ increase first and then decrease. Compared with other samples, the 800${}^{\circ }$C sintered samples had the highest saturation magnetization (59.03 emu/g), remanent magnetization (30.65 emu/g) and squareness (0.519). The increasing peak height of $dM/dH$ at $H_m$ indicates that the cubic spinel structure samples have good crystallinity and magnetic stability.

In this experiment, samarium ion was doping into nickel–copper–cobalt ferrite system by sol–gel self-propagation. The prepared chemical formula is ${\mathrm{\text{Ni}}}_{0.2}{\mathrm{\text{Cu}}}_{0.2}{\mathrm{\text{Co}}}_{0.6}$-${\mathrm{\text{Fe}}}_{2-x}{\mathrm{\text{Sm}}}_x{\mathrm{\text{O}}}_4$ ($x=0.0$, 0.025, 0.05, 0.075 and 0.1). The X-ray diffraction (XRD) analysis of the samples confirms the formation of a cubic spinel structure. The average crystallite sizes are about 66–88 nm for all the prepared samples. Fourier transform infrared spectroscopy (FTIR) measurements showed all the prepared samples had Fe–O absorption peaks. This finding further confirms that the prepared sample has a spinel structure. The morphological changes of the samples were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). According to the characterization results, the surface morphology shows spherical grains. Energy-dispersive X-ray spectroscopy (EDX) test results showed that the as-prepared pure samples contained Ni, Cu, Co, Fe elements, whereas other samples contained Sm elements and the contents were different. This indicates that the prepared samples are purer and the doping amount has been increased. The magnetic parameters of samples were measured by vibration sample magnetometer (VSM) at room temperature. The analysis of magnetic parameters shows that the saturation magnetization $(M_s)$ and remanent magnetization $(M_r)$ of the sample decrease with the increase of the doping amount of samarium ions. From the magnetic parameters, it can be concluded that ${\mathrm{\text{Sm}}}^{3+}$-doped Ni–Cu–Co ferrites have low magnetic properties.

In this paper, nickel nitrate, copper nitrate, cobalt nitrate, ferric nitrate were used as raw materials, citric acid was used as a complexing agent, and chromium nitrate was used as a modifier to synthesize ${\mathrm{\text{Ni}}}_{0.2}{\mathrm{\text{Cu}}}_{0.2}{\mathrm{\text{Co}}}_{0.6}{\mathrm{\text{Cr}}}_x{\mathrm{\text{Fe}}}_{2-x}{\mathrm{\text{O}}}_4$ by sol–gel method. The sample was characterized. X-ray diffraction (XRD) data on the sample showed that the particle size of the sample was 52.14–54.88 nm. The lattice constant varied from 8.3569 Å to 8.3758 Å. The data of Fourier infrared showed that the sample did not change with the structure of the doped sample of Cr ion and remained as the spinel type. It can be seen by SEM that the sample is irregularly spherical. Due to the doping of chromium ions, it appears agglomerated. Analysis of the elements of the sample by EDAX revealed that the sample contained Ni, Cu, Co, Fe, O and a peak corresponding to the Cr element was found in the sample having crion content of 0.025, 0.050, 0.075 and 0.100. The magnetic properties of the samples were characterized using VSM. The data are processed to obtain magnetic parameters such as saturation magnetization and coercivity.

Lanthanide-based manganite perovskites due to their possible integration both in conventional Si-based electronics, and in innovative full-oxide electronics, have led to a massive resurgence of interest. The properties and applicability of these perovskites can be tailored with the interplay of foreign ion substation, and thus lot of efforts have been made by the researchers by using various types of compound combinations. In this work, a systematic study of Ba-substituted lanthanide of a chemical formula La${}_{0.57}$Sm${}_{0.1}$Sr${}_{0.33-}{}_x$Ba${}_x$MnO₃ (where, $x=0.0$, 0.05, 0.1, 0.20 and 0.33) was done and the manganites were synthesized by sol–gel auto-combustion method. The structural and magnetic properties were investigated by thermogravimetric/differential thermal analysis, which was also carried out to investigate the thermal stability of the prepared samples. X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM), scanning electron microscopy (SEM) etc. were employed to investigate the crystallographic structure. XRD patterns and selected area electron diffraction patterns revealed the formation of single-phase La${}_{0.57}$Sm${}_{0.1}$Sr${}_{0.33-}{}_x$Ba${}_x$MnO₃ perovskite materials without any signature of secondary phases. Elemental composition of the synthesized samples was investigated by the energy dispersive analysis of X-ray analysis, which confirmed the expected stoichiometry of the prepared samples. TEM and SEM observations revealed the nano-crystalline nature of the prepared samples, where particle size obtained from TEM ranges from 40nm to 70nm. It has been found that structural and magnetic properties of the parent La${}_{0.57}$Sm${}_{0.1}$Sr${}_{0.33}$MnO₃ system were greatly affected by the Ba substitution.

In this research Sr-hexaferrite powder was synthesized by a sol–gel auto-combustion route using two different fuels (glycine and citric acid) and two different basic agents (ammonia and trimethylamine). N-decyltrimethylammonium bromide (C₁₃H₃₀BrN) was also employed as a cationic surfactant. The results showed the finest crystallite size and the lowest calcination temperature have been obtained as 27.2 nm and 800 °C respectively, in the presence of citric acid, trimethylamine and surfactant.

In this research SrFe₁₂O₁₉ nanocrystalline synthesized by sol-gel auto-combustion method and subsequent annealing at 1000°C for 1h subjected to mechanochemical treatment in a high-energy ball mill and then re-annealing. A planetary ball mill (Fritsch Pulveristte 6) was used to mill the strontium hexaferrite powder at 300 rpm in air for 10, 20 and 40 hours. The process was studied by X-ray diffraction technique and scanning electron microscopy. The X-ray study showed that SrFe₁₂O₁₉ phase was decomposed by milling. Strontium hexaferrite and α-Fe₂O₃ were obtained with 10 hours milling. There were α-Fe₂O₃ and strontium hexaferrite in XRD patterns of 20 hours milled sample. With increasing of the milling time to 40 hours, strontium hexaferrite was decomposed completely. The annealing of the 20 and 40 h milled powders at 900°C for 1h led to the formation of single phase strontium hexaferrite with smaller crystallite size compare to that of the hexaferrite powder before milling and subsequent annealing.