Search

With the development of science and technology, the research on magnetic materials is particularly important. In particular, the application of nanomagnetic materials in computer chips, magnetic recording, and biomedical fields has high research value. In this paper, Ni–Cu–Co ferrite nanomagnetic materials doped with rare earth (RE = Y3+, Sm3+, La3+ and Yb3+) ions were prepared by sol–gel auto-combustion method. The spinel structure of the sample was analyzed by X-ray diffraction (XRD), and the average crystallite size of the doped rare earth ions was calculated by the half width of (311) peak. The samples were further characterized by Fourier-transform infrared spectroscopy (FT-IR). Two characteristic peaks are at the wave number of 603 cm−1 and 391 cm−1, respectively. The morphology of the nanomagnetic grains was observed by scanning electron microscopy (SEM), and it was found that the nanomagnetic grains of the samples were all spherical or quasi spherical structure with water chestnut. Transmission electron microscopy (TEM) was used to observe the pure samples and Y3+ ion-doped samples. Through EDS analysis, it is found that the chemical composition of the sample is Ni, Cu, Co, Fe, O, Y, Sm, La, and Yb. Through vibration sample magnetometer (VSM) analysis, the samples of Ni–Cu–Co ferrite doped with different RE3+ ions have the characteristics of ferromagnetism.

In this study, yttrium ion-doped nickel–magnesium–cobalt ferrite powder was prepared by the sol–gel auto combustions method. The chemical formula is Ni0.2Mg0.1Co0.7Fe2–xYxO4 (where x = 0.00, 0.02, 0.04, 0.06, and 0.08). The structure and magnetic properties were studied by X-ray diffractometer (XRD), Fourier infrared spectroscopy (FTIR), ultraviolet–visible (UV–Vis), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM). XRD measurements show that Ni–Mg–Co ferrite has a good phase formations, and all samples have single-phase cubic spinel structure. As the doping amount of yttrium ions increases, the lattice constant of the samples increases first and then decreases. FTIR measurements also confirm the formations of the cubic spinel structure of ferrite. The UV–Vis optical analysis shows that the bandgap value of optical energy decreases after doping Y3+ ions. SEM confirmed that the sample was spherical spinel with a particle size of 54–60 nm. The saturation magnetizations (Ms) and remanent magnetizations (Mr) increase first and then decrease with the increase of Y3+ ions content at room temperature. This shows that the small amount of Y3+ ions-doped nickel–magnesium–cobalt nanoferrite can optimize the magnetic properties of the ferrite. The coercivity of the samples also showed a downward trend. The comprehensive measurement data show that the sample has the best magnetic properties when x = 0.02. This is also confirmed that the ferrite can be used as magnetic storage material.

In this paper, Bi3+ ion-doped Ni–Mg–Co ferrite nanomagnetic materials were prepared by sol–gel auto-combustion method using high-purity nitrates and citric acid experimental materials. The effect of Bi3+ ion content on the lattice structure and magnetic properties of nanoferrite was also studied. XRD diffractogram analysis shows that the Ni–Mg–Co ferrite samples with x = 0 and 0.025 have single-phase cubic spinel structure. It is found that when the doping amount is 0.05 or >0.05, the secondary-phase Bi2O3 peak appears. The average crystallite size of the sample was calculated by Debye–Scheller formula. It was found that the average grain size of the sample was affected by the doping concentration. With the increase in Bi3+ ion content, the average crystallite size increases from 8.3797 nm to 8.3940 nm. The structure of Bi3+ ion-doped Ni–Mg–Co ferrite was further characterized by FT-IR. There are two absorption bands ν1 and ν2 at 584 and 397 cm−1, which further prove the spinel structure. The morphology of the sample particles was observed by SEM, and the distribution of the particle size was calculated. The chemical components of powder samples were analyzed by EDS. Through VSM analysis, the Bi3+ ion-doped Ni–Mg–Co ferrite has the characteristics of ferromagnetism. With the increase in Bi3+ ion content, the residual and saturation magnetization decreased; the magnetic stability is also reduced. The results show that the magnetic properties of Bi3+ion-doped Ni–Mg–Co ferrite are decreased.

Sol–gel auto-combustion method was used to prepare ferrite nanoparticles with the chemical composition of Ni0.2Cu0.1Co0.7Fe2−xCexO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1). Diverse technique characterizations reveal that all samples are spinel structures. It was observed that the ferrite nanoparticles were spherical and cubic. When the doping content of Ce3+ ion is x = 0.025, compared with other doped samples and pure samples, the samples have better magnetic properties and also the largest square degree (Mr/Ms) and coercivity rectangle degree (S*). This also shows that a small amount of rare-earth Ce3+ ion doping can improve the magnetic properties of the samples. And the prepared ferrite can be used for magnetic recording and magnetic storage.

A series of ferrite samples with the compositional formula, Ni0.2ZnxCo0.8−xFe2O4 (x = 0.0, 0.2, 0.4, 0.6 and 0.8), was prepared using the citrate-based sol–gel method for the better understanding of zinc doping on the structural and magnetic properties. X-ray diffraction (XRD) studies of the samples showed single-phase ferrite cubic structure without any secondary phases, with the average crystallite size D = 103–130 nm for the samples heat-treated at 950 °C. TEM micrograph shows nearly sphere-shaped particles with particle size consistent with the XRD results. The lattice parameter increased linearly with increasing Zn2+ ion content. Fourier transform infrared (FT-IR) measurements also confirm the formation of the cubic spinel structure of ferrite. The ferrite samples were observed by scanning electron microscopy (SEM) to be spherical nanoparticles. The surface morphology and stoichiometric ratio of the compositional elements were analyzed by scanning electron microscopy equipped with energy-dispersive spectroscopy (EDS). EDS showed that the elemental ratios were stoichiometric. The static magnetism of the magnetometer was studied by using a vibrating sample magnetometer (VSM). An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Zn concentration up to x = 0.2 and a decrease thereafter. These results could be explained using Neel’s collinear two-sub-lattice model and three-sub-lattice non-collinear model suggested by Yafet and Kittel. The magnetic cubic anisotropy constant determined by the law of approach to saturation decreased with increasing Zn content. For Zn-substituted Ni–Co ferrites, the magnetic properties decrease obviously with the increase in Zn2+ ion content. This rapid decrease in magnetic properties reveals that the magnetic properties of Zn-substituted nickel–cobalt ferrite have realized the transition from hard magnetism to soft magnetism. The smaller coercivity value confirms that soft ferrite has been obtained. Meanwhile, this transition from hard magnetism to soft magnetism can be used as a potential high-frequency soft magnetic material.

Manganese substituted nickel–cobalt ferrite nanoparticles having the basic composition Ni0.2MnxCo0.8−xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized using sol–gel auto combustion method. The effect of Mn substitution on structural and magnetic properties of nickel–cobalt ferrite has been studied. All the prepared samples show that the single-phase cubic spinel structure by X-ray diffraction. The average microcrystalline size of the prepared samples is about 50 nm calculated by Scherrer equation. With the increase of Mn content, the lattice constant decreases first and then increases for the prepared samples. Fourier transform infrared measurements also confirm the formation of the cubic spinel structure of ferrite. The absorption peak of the Fe–O bond at tetrahedral position shifted to the low frequency with the increase of manganese ion content. By transmission electron microscope observation of the preparation of samples with spherical cube crystallite particles. Energy dispersive X-ray confirmed that the synthesis with pure phase and structure of ferrite, and successfully realized the Mn2+ doping. Vibration sample magnetometer measurement confirm that the Ni0.2MnxCo0.8−xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4) nanoparticles have ferromagnetic behavior. It is observed that the saturation magnetization (Ms), remanent magnetization (Mr), rectangular ratio (Mr/Ms) and magnetic moment are decreasing with the increase of manganese ion content. The prepared ferrites have high coercivity, and the decrease of coercivity of samples is due to excessive Mn substitution. At the same time, the magnetization is expected to decrease because of the conversion of equivalent amounts of Fe3+ (5 µB) to Fe2+ (4 µB).

In this paper, a two-dimensional(2D) parallel optical extinction experiment system was adopted. The ethanol gasoline was selected as the fuel, which was blended with 20% ethanol. The laminar diffus...

In order to investigate the effect of sintering temperature on the structure and properties of Zn–Co ferrite, the Zn0.5Co0.5Fe2O4 ferrite powder with spinel structured was prepared by sol–gel method at different sintering temperatures. X-ray diffraction spectroscopy (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) were used to study the structural and magnetic properties of the prepared samples. It was found that the sintering temperature has a significant influence on the structure and magnetic properties of the Zn–Co ferrite. As the sintering temperature increases from 600 to 1000 °C, the crystallinity and crystallite size of the samples increase significantly, but the coercivity, remanence, and squareness decrease and the saturation magnetization increases first and then decreases. Compared with other samples, the sample sintered at 900 °C has the highest bulk density (3715.42 kg/m3) and saturation magnetization (68.17 emu/g). At the same time, it also has a small coercivity, remanence, anisotropy constant, and porosity. The sample obtained by sintering at 800 °C has a good magnetic susceptibility (dM/dH) at Hm. This work provides basic research data for the preparation of Zn–Co ferrite with better magnetic properties and has certain reference value.

The Miller cycle with EIVC is applied to a medium-speed marine diesel engine to achieve high-efficiency combustion and low nitrogen oxide (NOx) emissions. The effects of Miller cycle on the state parameters, combustion characteristics, NO emissions, and the spatial distribution of working fluid were analyzed. A one-dimensional (1D) simulation model was established by using the BOOST software. The FIRE software was used to simulate the combustion process and emission characteristics of the diesel engine at medium and low loads. The results show that in the E3 cycle (four kinds of loads, 100%, 75%, 50%, 25%, according to Marine application propeller law), with the proper EIVC, the in-cylinder pressure, temperature and NO emission will be reduced. At the load of 50%, NO emissions were reduced by 17.8%, At 25% load NO emissions were reduced by 14.9%. During the fuel injection, the decrease of in-cylinder temperature causes a longer ignition delay period. When the EIVC is too early, the heat release rate increases sharply, at the same time, the NO generation also increases. Furthermore, it will lead to misfire at low load.

Lanthanum doped Ni–Cu–Co nano ferrites with the chemical composition Ni0.2Cu0.1Co0.7Fe2−xLaxO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1) were prepared by sol–gel auto-combustion technology. All samples were sintered at a temperature of 950 ℃. The X-ray diffraction (XRD) analysis verifies that all the samples of the formation of the cubic spinel structure. It turns out that with the addition of La3+ ions, the lattice constant decreases, and with the addition of La3+ ions, the lattice constant increases. The obtained Fourier transform infrared (FT-IR) measurement also confirms the formation of the spinel structure. With the increase in La, the higher frequency ν1 is slightly moving toward the high-frequency side. Transmission electron microscopy (TEM) images show the presence of particles, which are spherically cubic shaped crystallites. The presence of constituent’s, i.e., the presence of ingredients, namely, Ni, Cu, Co, Fe and La were authenticated by energy dispersive X-ray analysis (EDX). It was confirmed La3+-doping was successfully achieved. The magnetic parameters were measured by Vibrating sample magnetometer (VSM). The saturation magnetization, remanent magnetization, coercivity, anisotropy constant first increase and then decrease with the La content increases. The sample had the best magnetic properties when the doping content of La at x = 0.025. This indicates that appropriate doping can improve the magnetic properties of the samples. The reduction of the magnetic moment can be attributed to non-magnetic La3+ ions in place of Fe3+ ions (5µB), which results in a reduction of net total magnetic moment.

Sol-gel auto-combustion is a method of preparing ferrite by combining combustion with chemical gel. In this study, Ni-Mg-Co ferrite powders are prepared by coprecipitation method, and the nanocrystals of Ni0.2MgxCo0.8−xFe2O4 are successfully synthesized. The structure and magnetic properties of undoped and Mg-substituted Ni-Co ferrite nanoparticles are systematically investigated. The methods used to characterize the prepared samples are X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and Vibrating sample magnetometry (VSM). The synthesized samples are confirmed by XRD analysis to form a single-phase cubic spinel structure with crystals between 48 and 50 nm. With the increase of Mg ion concentration, the lattice constant decreases. The results of FTIR spectroscopy indicated that a spinel structure was formed. Transmission electron microscopy (TEM) images show spherical cubic microcrystals in the samples. EDX analysis confirms that the synthesized ferrite is pure phase structure, and Mg2+ is successfully replaced. With the increase of Mg2+ ion content, the saturation magnetization and remanent magnetization decreased from 70.16 to 39.77 emu/g and 36.40 to 20.20 emu/g at room temperature, respectively. Meanwhile, the coercivity decreases from 1032.16 to 378.50 Oe by increasing Mg2+ concentration. This also indicates that the Mg-substituted Ni-Co nano-ferrite has a low magnetic of multi-ferric material. The increasing of peak height of dM/dH at Hm indicates that the cubic spinel structure sample has good crystallinity and magnetic stability.

Bismuth doped Ni–Cu–Co nano ferrites with the chemical composition Ni0.2Cu0.2Co0.6Fe2−xBixO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1) were prepared by sol–gel auto-combustion technology. The analysis of the X-ray diffraction (XRD) patterns confirms that all the samples have a cubic spinel structure. The particle sizes of the prepared samples (between 51 and 55 nm) are determined by the Scherrer equation. The obtained Fourier transform infrared measurement also confirms the formation of the spinel structure. It was observed that with the increase of Bi3+ ion concentration, the protruding absorption band was slightly shifted to the high frequency side. Transmission electron microscopy images show the presence of particles which are spherically cubic shaped crystallites. It has been proved that the synthesized ferrite has pure phase and structure by Energy dispersive X-ray, and Bi3+-doping was successfully achieved. Cation redistribution in spinel ferrite nanoparticles are confirmed by X-ray photoelectron spectroscopy (XPS). The magnetic parameters of the samples are measured by Vibration sample magnetometer (VSM) at room temperature with a maximum magnetic field of 1 T. It can be clearly observed that the magnetic properties such as saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) decrease significantly with the bismuth ion concentration increases. This is because Bi3+ ions replace Fe3+ ions, and Bi3+–Fe3+ ion interactions are more predominates than Fe2+–Fe3+ ion interactions. This also indicates that the bismuth doped nickel copper cobalt ferrite has low magnetic properties.

In this paper, the two-dimensional parallel light extinction method was carried out to study the soot formation in laminar diffusion flames of four different ethanol-gasoline blends, of which ethanol volume fractions ranging from 0% up to 100% (E0, E20, E80, and E100). The flame images were processed synthetically via matlab to accurately calculate the flame height. In addition, the flame structure was redefined as three zones to observe the soot formation. The results indicate that the flame height changes with the variation of gas volume flowrate and fuel mass flowrate during the experiment. In terms of soot formation, as the volume fraction of ethanol increases, the proportion of soot forming zone decreases, while the area of blue flame zone grows. Simultaneously, the transition zone accounts for about 21% of the total flame area, which has no significant change with the increase of ethanol volume fraction.

The main purpose of this experiment is mainly to explore the magnetic properties and nano-structure of magnesium-cobalt ferrite. The magnesium-cobalt ferrite was prepare by sol–gel self-propagation method. During the preparation of the sample, we considered the effect of pH in solution of the magnetic properties and nano-structure of the magnesium-cobalt ferrite by changing the pH value of the precursor solution. Eight distinct characteristic peaks can be observed in the XRD map, which indicates that the prepared sample has a spinel structure. There are characteristic peaks (Me–O) in the Fourier infrared spectrum, and it changes with the preparation conditions. This indicates that the microstructure of the sample changes due to the change of preparation conditions. The EPMA test showed that the prepared sample had chemical elements such as magnesium, cobalt, iron, and oxygen, which confirmed that the sample was a relatively pure mixture. This result was in agreement with the fact that there was no obvious impurity peak in the XRD spectrum. Quantitative analysis of the chemical elements in the sample shows that the proportion of each component is similar to the target product. The SEM characterization indicates that the sample has a circular or elliptical surface structure and that the sample particles are evenly distributed. The VSM characterization results show that the pH of the solution has a major impact on the magnetic properties of magnesium-cobalt ferrite. Therefore, the pH value of the precursor should be strictly controlled in the preparation of ferrite, so as to prepare ferrite materials with better magnetic properties.

In this paper, Al3+ ion substituted Ni–Mg–Co ferrite nano-magnetic material by sol–gel auto-combustion method. Citric acid is used as a complexing agent, and high-purity nitrate and deionized water are used as raw materials. And the effect of Al3+ ion substitution on the structure and magnetic properties of Ni–Mg–Co ferrite nanoparticles was studied. XRD analysis showed that all the samples have the characteristic peak of spinel ferrite. No impurity peaks were found, indicating that the ferrite has a single-phase structure. The average crystallite size was calculated by Debye–Scheller formula. With the increase of Al3+ ion substitution, the average crystallite size decreased from 58.3378 to 51.5249 nm. The structure of Ni–Mg–Co ferrite was characterized by FT-IR. There are two absorption bands ν1 and ν2 at 588 cm−1 and 389 cm−1, respectively, which further prove the spinel structure. The morphology of the samples was observed by SEM, and the particle size of the nanoparticles was calculated. The chemical composition of the sample was analyzed by EDS. The elements Ni, Mg, Co, Fe, Al, and O were found in the samples. By VSM analysis, it is found that Al3+ ion-substituted Ni–Mg–Co ferrite has ferromagnetic characteristics. With the increase of Al3+ ions substitution, the remanent magnetization (Mr), saturation magnetization (Ms), coercive force (Hc), anisotropy constant (K), magnetic moment (μB), and Yafet–Kittel angle (αYK) all decreased.

This correction is a clarification on the work reported, due to comments the editorial office has received.

The use of renewable alternative fuels in diesel engines has grown recently. In order to study the effects of different swirl ratios (SRs) on the performance of a diesel engine fueled with ...

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 [Formula: see text] 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.

Zinc substituted magnesium-cobalt ferrite nanoparticles having the basic composition Mg0.2Co0.8−xZnxFe2O4 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) were successfully synthesized using sol–gel auto combustion method. The results show that the doping amount of Zn2+ ions has a great influence on its structure and magnetic properties. X-ray diffraction (XRD) measurements show that Mg0.2Co0.8−xZnxFe2O4 has a good phase formation, and all samples have single-phase cubic spinel structure. The average crystallite size is calculated from Scheller's formula to be between 49 and 54 nm. And the lattice constant increases from 8.38 to 8.43 A with the increase of Zn2+ ions content. Fourier transform infrared (FTIR) measurements also confirm the formation of the cubic spinel structure of ferrite. The ferrite samples were observed by scanning electron microscopy (SEM) to be spherical nanoparticles. The magnetic properties of the samples have been determined at room temperature by vibrating sample magnetometer (VSM). The results show that the magnetic properties of Mg-Co ferrite are significantly affected by the doping amount of Zn2+ ions. For Zn-substituted Mg-Co ferrites, the magnetic properties decrease obviously with the increase of Zn content. This rapid decrease of magnetic properties reveals that the magnetic properties of Zn-substituted magnesium-cobalt ferrite have realized the transition from hard magnetic to soft magnetic. Meanwhile, the coercivity is Hc = 21.26 Oe, the saturation magnetization is 4.56 emu/g and the remanent magnetization is 0.03 emu/g for Mg0.2Zn0.8Fe2O4 sample. This also indicates that the ferrite samples prepared have a transition from ferromagnetic behavior to superparamagnetic behavior. The smaller coercivity value confirms that soft ferrite has been obtained. Meanwhile, this transition from hard magnetism to soft magnetism can be used as a potential high frequency soft magnetic material.

In this experiment, samarium ion was doping into nickel–copper–cobalt ferrite system by sol–gel self-propagation. The prepared chemical formula is [Formula: see text]-[Formula: see text] ([Formula: see text], 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 [Formula: see text] and remanent magnetization [Formula: see text] of the sample decrease with the increase of the doping amount of samarium ions. From the magnetic parameters, it can be concluded that [Formula: see text]-doped Ni–Cu–Co ferrites have low magnetic properties.

Sol-gel auto combustion method (EDTA, egg white, oxalic acid, tartaric acid and citric acid as a complexing agent) was used to prepare Ni–Cu–Co ferrite nanoparticles with the chemical composition of Ni0.2Cu0.1Co0.7Fe2O4. The phase formation has been confirmed by XRD patterns, which is a characteristic of spinel ferrite with most intense (311) peak. The crystallization of the material in the cubic spinel structure, the lattice parameter is approximately 8.38 A. The average crystallite size of the samples prepared with different complexing agents ranged from 30 to 40 nm. The formation of spinel structure was also confirmed by Fourier transform infrared (FTIR) measurements. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images indicate the existence of spherically cubic shaped particles. The synthesized samples were demonstrated by energy dispersive X-ray (EDX) to have pure phase and structure, Ni, Cu, Co, Fe, and O were the main elements in Ni0.2Cu0.1Co0.7Fe2O4. Confirmed by X-ray photoelectron spectroscopy (XPS) cation redistribution of spinel ferrite nanoparticles. The magnetic parameters were measured by Vibrating sample magnetometer (VSM). Their ferromagnetic behavior was confirmed by observing the hysteresis loops of the samples. Compared with the samples prepared with other complexing agents (EDTA, egg white, tartaric acid and citric acid as complexing agents), the maximum of saturation magnetization and remanent magnetization were obtained for the sample prepared with oxalic acid as complexing agent. These ferrites have high coercivity. The sample prepared with oxalic acid has better magnetic properties than those samples prepared with other complexing agents. This indicates that oxalic acid as a complexing agent has stronger complexing ability for samples and less hydrolysis of metal ions in precursor solution than other complexing agents.

In this paper, aluminum-doped Ni–Cu–Co ferrite nanomagnetic material powder was prepared by sol–gel technique using citric acid as a complexing agent and high-purity nitrate as raw material. The effect of doping amount of different Al[Formula: see text] ions on the structure and magnetic properties of ferrites has been studied. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Energy dispersive X-ray (EDX) and Vibrating sample magnetometer (VSM) were used to characterize the structural and magnetic properties of ferrite. The XRD analysis showed that all samples of Ni–Cu–Co ferrites have a single-phase cubic spinel structure. Average crystallite size was calculated by the Debye–Scherrer formula and it was found that the average crystallite size of the sample was affected by the doping concentration. As the amount of Al[Formula: see text] ion doping increases, the crystallite size decreases from 54.88 nm to 46.09 nm. The absorption peak of Fourier transform infrared spectroscopy (FTIR) at 590 cm[Formula: see text] further indicates the formation of cubic spinel structure of Ni–Cu–Co ferrite. Transmission electron microscopy (TEM) images show the presence of particles which are spherically cubic-shaped particles. The constituent elements of the samples were analyzed by EDX spectroscopy. In addition, the ferromagnetism of the samples was confirmed by VSM measurements. The saturation magnetization (Ms) and remanent magnetization (Mr) first increase and then decrease when the aluminum ion concentration increases. Compared with pure samples and other doped samples, they have the best magnetic properties when the doping amount of Al[Formula: see text] ions is [Formula: see text]. It also shows that the prepared samples are suitable for magnetic recording materials.

In order to study the effect of sintering temperature on the structure and magnetic properties of nickel-magnesium-cobalt ferrite, [Formula: see text] spinel ferrite with different sintering temperatures (500[Formula: see text]C, 600[Formula: see text]C, 700[Formula: see text]C, 800[Formula: see text]C, 900[Formula: see text]C and 1000[Formula: see text]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[Formula: see text]C to 1000[Formula: see text]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 [Formula: see text] increase first and then decrease. Compared with other samples, the 800[Formula: see text]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 [Formula: see text] at [Formula: see text] indicates that the cubic spinel structure samples have good crystallinity and magnetic stability.

Manganese substituted nickel–copper–cobalt ferrite nanoparticles having the basic composition [Formula: see text] (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[Formula: see text] ion substituted in nickel–copper–cobalt ferrite were studied by Vibrating sample magnetometer (VSM). The saturation magnetization ([Formula: see text]), remanent magnetization [Formula: see text], coercivity [Formula: see text], magnetic moment [Formula: see text] and anisotropy constant [Formula: see text] first increase and then decrease with the increase of [Formula: see text] ions content. They had better magnetism than pure sample and other substituted samples when the substitution amount of [Formula: see text] ions was [Formula: see text]. At [Formula: see text], the maximum values of remanent magnetization [Formula: see text], saturation magnetization [Formula: see text] and coercivity [Formula: see text] 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 [Formula: see text] ions instead, ferrite magnetism is weakened. This means that these materials can be used in magnetic data storage and recording media.

In this work, sol–gel auto-combustion technology is used to synthesize nanocrystalline Ni[Formula: see text]Cu[Formula: see text]Co[Formula: see text]Fe2O4 with high purity metal nitrate and citric acid as precursor solution. The prepared samples are sintered at different temperatures (400[Formula: see text]C, 500[Formula: see text]C, 600[Formula: see text]C, 700[Formula: see text]C, 800[Formula: see text]C, 900[Formula: see text]C, 1000[Formula: see text]C and 1100[Formula: see text]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[Formula: see text]. 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[Formula: see text]C to 700[Formula: see text]C. The dM/dH versus H curves are obtained by differentiating the hysteresis loop. The increasing peak height of dM/dH at [Formula: see text], indicates a magnetically stable state for the samples with good crystalline cubic spinel structure.