Magnetoplumbite Phase Research Articles

Exploring the structural, optical, dielectric and magnetic properties of rare earth samarium doped Ca-Mg based Ca0.5Mg0.5Fe12−xSmxO19 ferrite nanoparticles

The emergence of M-type hexaferrite presents an encouraging alternative to rare earth magnets, due to its economic feasibility and outstanding magnetic properties. This makes it a viable option for applications in the electric automotive and magnetic industry applications. In this study, we utilized a sol–gel auto-combustion technique to synthesize a series of samarium (Sm) doped calcium-magnesium (Ca-Mg) hexaferrite samples having chemical formula Ca0.5Mg0.5Fe12−xSmxO19 (x = 0.00, 0.05, 0.10, 0.15, and 0.20). The XRD analysis confirmed the crystal structure of the synthesized materials, revealing a consistent magneto-plumbite phase across all samples. Scanning electron microscopy (SEM) investigations further confirmed the homogeneous distribution and agglomeration of nanostructures. FTIR analysis identified the presence of two primary absorption bands in Ca-Mg hexaferrites with both bands exhibiting a shift towards lower frequency ranges with increasing doping levels. The dielectric loss (ε″) and dielectric constant (ε′) were higher at lower frequencies but decreased as the frequency increased. Additionally, higher concentrations of samarium resulted in further reductions in both dielectric loss (ε″) and dielectric constant (ε′). Notably, saturation magnetization (Ms) and remanence (Mr) values demonstrated an increasing trend with higher degrees of Sm+3 substitution, while coercivity (Hc) values exhibited relative stability. Our findings indicate that these materials possess promising magnetic parameters falling within the ranges of 31.52–37.77 emu·g−1 for Ms, 18.16–21.53 emu·g−1 for Mr, and 2.088–2.243 kOe for Hc, suggesting their potential utility across diverse applications including permanent magnets used in electric vehicle motors, storage devices, microwave components, and electromagnetic radiation absorbers.

Samarium substituted M-type Ca-hexaferrites: Structural and magnetic features

In this work, the sol–gel combustion method was used to fabricate a series of rare earth samarium doped Ca-hexaferrites (CaFe12-xSmxO19). X-ray diffraction was used to explore the structural insights. The structural analysis confirmed the magnetoplumbite phase throughout all compositions with the expansion in the lattice. Furthermore, microstructural analysis showed an increase in X-ray density and a decrease in porosity and dislocation density with increasing doping levels, respectively. Morphology confirmed the uniform distribution of particles throughout all the fabricated samples. The crystallite size was determined from X-ray diffraction data and ranges between 48.28–55.52 nm. Magnetic parameters such as remanence and saturation magnetization showed an increase from 25.27 emu/g to 44.029 emu/g, while coercivity values dropped from 3.301 kOe to 2.334 kOe causing significant deviations in the magnetic moment per formula unit μB (mB), Anisotropy field (Ha), and anisotropy parameter (B). The materials were shown to have promising magnetic characteristics for storage applications.

Sintering temperature optimization for enhanced magnetic performance in La–Ca–Co doped strontium ferrite

The effectiveness of employing La-Ca-Co co-doping has been demonstrated as the optimal approach for enhancing the magnetic performance of strontium ferrite. However, limited studies have explored the evolution of the magnetoplumbite phase and its correlation with the sintering temperature. In our research, La-Ca-Co doped strontium ferrite permanent magnets were fabricated using a conventional ceramic process and a two-step sintering technique. After sintering at different temperatures, all the samples possess proper c-axis orientation. When the sintering temperature was raised from 1175 °C to 1205 °C, there was an upward trend observed in the remanence Br, increasing from 430 mT to 439 mT. The coercivity Hcj exhibited an increase from 380 kA/m and reached its peak at 397 kA/m at 1185 °C. Although the Br value remained favorable, the coercivity experienced substantial deterioration, reaching its lowest point at 303 kA/m at 1205 °C. Under a sintering temperature of 1195 oC, magnetic performance with optimal energy product was achieved, with Br of 439 mT, Hcj of 379 kA/m, Hcb of 318 kA/m, and (BH)max of 35.5 kJm-3.

Enhanced X-band absorption and shielding performance of Gd-substituted barium hexaferrite

Gd- substituted barium hexaferrite has been synthesized by solid-state ceramic method to explore its X-band (8.2 – 12.4 GHz) absorption and shielding performance. The structural, magnetic, and microwave properties of the synthesized hexaferrite were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and vector network analyzer (VNA). XRD patterns confirmed the hexagonal magnetoplumbite phase formation in all samples. A noticeable red shift in the Raman spectra from 710 to 705 cm-1 and 323–327 cm-1 suggested the presence of Fe2+ ions at 4f1 tetrahedral and 12k octahedral sites, respectively. Microstructural studies on as-prepared samples confirm particle size reduction up to 1.86 µm with Gd substitution. A modest increase in magnetization and remanence value for 20% Gd was noted. Coercivity increased with substitution, whereas the anisotropy field and crystalline anisotropy constant reduced with Gd addition. An overall improvement in shielding efficiency and absorption was noted for Gd- substituted samples. A maximum average shielding efficiency of 16.47 dB and effective absorption of 99.99% was recorded for 10% Gd. Overall, microwave absorbance is improved up to 97% with Gd substitution, which suggests this material can also work as an absorber in microwave device applications.

Enhanced magnetic properties in Sm3+ substituted SrFe12O19

M- Type hexaferrite captivates researchers and industrialists for its diverse usage and applications in different fields such as permanent magnets, storage devices, recording media, radar absorbing materials and many more. In this work, Sm3+ substituted Strontium hexaferrite, Sr1-xSmxFe12O19 (x = 0, 0.05) is synthesized by using ethylene glycol aided sol–gel auto combustion technique. X-Ray Diffraction Technique is employed for the understanding of various structural features. Phase purity of the prepared samples is authenticated by performing Rietveld refinement method. All the studied samples crystallizes in hexagonal magneto-plumbite phase with P63/mmc space group. Crystallite sizes are determined using Scherer equation. Field Emission Scanning Electron Microscopy is used for morphological analysis. Average particle size decreases with Sm3+ substitution in comparison with parent one. Both field and temperature dependent magnetization measurements are accomplished for magnetic properties analysis. Hysteresis curves show Coercivity (Hc) value increases more than two times and saturation magnetization (MS) decreases slightly as compared to parent sample which clearly indicates that the sample can be used as hard ferrites. M−T measurements are carried out with the application of 500 Oe field. Both the sample show transition around 500 °C temperature. Substituted sample also shows a prominent Hopkinson peak in comparison with parent sample.

Facile synthesis of Yb3+-Zn2+ substituted M type hexaferrites: Structural, electric and photocatalytic properties under visible light for methylene blue removal

Nanocrystalline M type hexaferrites Ca0.5Pb0.5-xYbxZnyFe12-yO19 (x = 0.00–0.1, y = 0.00–1.00) were synthesized by sol-gel autocombustion method. The effects of Yb-Zn doping on structural, optical and electric nature of Ca-Pb M type hexaferrites were explored. The crystal structure of the hexaferrites revealed magnetoplumbite phase with Yb-Zn varying contents (x, y) from 0.00 to 0.1 and 0.00 to 1.00. While the SEM confirmed the presence of well-developed flake shaped particles with size of 16–17 nm. Increase in the dielectric parameters from12.3 to 344.65 k has been observed by dielectric spectroscopy. The results demonstrate that band gap (2.6–2.5 eV) of CaPbFe12O19 can be tuned by the intervention of Yb and Zn ions to enhance the photocatalytic performance. The photocatalytic degradation of methylene blue (MB) dye with undoped CaPbFe12O19 and doped Ca0.5Pb0.5-xYbxZnyFe12-yO19 M type hexaferrites was performed at pH 07 varying time intervals from 0 to 90 min. The Ca0.5Pb0.5-xYbxZnyFe12-yO19 (x = 0.1, y = 1.00) exhibited enhanced percentage degradation efficiency 96.1 % at visible light irradiation in 90 min at pH 07 following the first order kinetics. On the basis of obtained results, Yb-Zn doped CaPbFe12O19 M type hexaferrites can be proposed as excellent material for dielectric, microwave and photocatalyst for the removal of textile contamination.

Microstructure and Magnetic Properties of M-Type Sr0.1Ca0.4La0.5Fe12O19 Ferrites: The Impact of Different Precursors

M-type Sr0.1Ca0.4La0.5Fe12O19 powder specimens doped with different precursors RFe2O4(R = Co, Ni, Cu, Zn, and Mg) were prepared via a traditional solid-state reaction method. The structural and magnetic properties of the specimens were studied. Only nthe single magnetoplumbite phase was found in all the specimens with uniformly distributed particles. The specimen with Zn-type precursor has the highest saturation (Ms), while the specimen with Co-type precursor has the highest remanent magnetism (Mr), coercivity (Hc), and the best comprehensive magnetic properties.

Synthesis, characterization, dielectric and magnetic properties of substituted Y-type hexaferrites

Fabrication of a series of zinc–strontium hexaferrites, Sr2Zn2−xMnxFe12−yHoyO22 (x = 0.0–1.0, y = 0.0–0.1) was carries out by chemical co-precipitation route with the aim to enhance the saturation magnetization and coercivity and decrease the resistivity to make the materials applicable for recording media of high-density applications. The synthesized hexaferrites were interpreted by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The results of XRD investigation certify the single magnetoplumbite phase formed in hexaferrites with regular crystallite particle size in the 31–38 nm range. Magnetic and dielectric properties of the hexaferrites were also observed. The dielectric parameters (dielectric loss also its tan loss and dielectric constant) were measured at ambient temperature and in 1.0 MHz to 3.0 GHz frequency range. These parameters of Mn–Ho-substituted Zn–Sr hexaferrites showed constant trend with frequency up to a certain value after that resonance sort of behavior was observed. In all the hexaferrites dielectric parameters initially decrease with frequency then become almost constant followed by resonance type behavior. The dielectric parameters of the synthesized samples decrease with dopant content initially but then increase up to maximum dopant level. The saturation magnetization (Ms) and remanence (Mr) increase as the dopant content increases due to magnetic substituents. The squareness ratios of all the nanomaterials synthesized in the present studies is less than 0.5. The coercivity (Hc) decreases by the substitution of Mn and Ho.

Study of Structural and Magnetic Properties of Co-doped M-Type Sr-Hexaferrite Nanoparticles

Abstract: The aim of this work is to synthesize nanocrystalline SrFe10Co3O19 with M-type hexaferrites via Sol-gel auto-combustion method. The synthesized powders were consequently subjected to calcination at 900oC for 6h. The synthesized samples are characterized by X-ray diffraction (XRD) to find structural parameters. The XRD results exposed single hexagonal magnetoplumbite phase formation in the heated samples. The morphology of the compound was revealed by Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Vibration Scanning Magnetometer (VSM) provides the magnetic nature of the compound. It shows that the decrease in coercivity was affected by doping of Co2+ ions. Keywords: M-type hexagonal ferrites, SEM, Sol-gel, VSM, XRD.

Effect of Gd doping on magnetic and MCE properties of M-type barium hexaferrite

Gd doped barium hexaferrite (BaFe12−xGdxO19, x = 0.0–0.7) has been synthesized by the sol-gel method to explore its magnetic and MCE (magnetocaloric effect) properties. The materials crystallize to hexagonal magnetoplumbite phase. Average particle size decreases with the increase in Gd concentration in barium hexaferrite (BHF). The coercive field increases from 3.2 to 4.8 kOe, and saturation magnetization decreases from 68.21 to 54.23 emu/g with the increase in Gd concentration from x = 0.0 to x = 0.7. These large changes in magnetic parameters reveal the effect of Gd concentration in BHF. The saturation magnetization monotonously reduces with an increase in Gd concentration in BHF due to a decrease in average particle sizes. The saturation magnetization is found to be higher at a lower temperature (60 K) compared to that of room temperature (300 K). It is due to a reduction in thermal energy at low temperature which is smaller compared to the magnetic Gibbs free energy at low temperature. Hence, the magnetic spins are freezing along the applied magnetic field direction at the low temperature. Also, the magnetocrystalline anisotropy constant (obtained by the "Law of Approach to Saturation method") is found to be more at low temperature compared to that of room temperature due to an increase in the strength of spin-orbit coupling with the decrease in temperature (i.e. thermal energy). The M-T curves and M-H hysteresis loops reveal paramagnetic to ferromagnetic transition at the Curie temperature. The maximum entropy change was found to be in the range of 0.12–0.72 J/kgK in a window of the applied magnetic field of 0.5–3 T, and the corresponding RCPmax was found to be 2.5–27.5 J/kg. The present study opens a window to explore the MCE on BHF based material.

Structural, optical, dielectric, and magnetic properties of Sr0.7La0.3Zn0.3Fe11.7–xAlxO19 hexaferrite synthesized by the solid-state reaction method

M-type Sr0.7La0.3Zn0.3Fe11.7–xAlxO19 hexaferrites were prepared using the conventional solid state reaction method in 1240 ​°C. XRD spectras indicated that there was a single magnetoplumbite phase with no detection of other phases for all samples. FT-IR and Raman spectra proves the formation of lattice and structure of M-type hexagonal ferrite respectively, and by the shift of the peaks, we speculate that Al3+ entered the lattice. FE-SEM micrographs showed that the grains were platelet-like shapes, EDS indicates that all elements are predetermined and no other elements are produced. The impedance analyzer found that all the dielectric parameters were optimized in different degrees under the corresponding doping amount, and the change was consistent with the characteristics of hexagonal ferrite magnetic materials. VSM finds that HC increased rapidly to a maximum value of 4576.8 ​Oe at x ​= ​1.5, which was ∼96.4% increase in coercivity as compared to that of Sr0.7La0.3Zn0.3AlxFe11.7-xO19 at x ​= ​0.0.

Synthesis, Magnetic and Electrical Characteristics of Ba‐Sr Hexaferrites Substituted with Samarium, Chromium and Aluminum

AbstractA series of M‐type Ba−Sr hexaferrites of composition Ba0.20Sr0.80‐xSmxFe12‐y(Cr0.5Al0.5)yO19 (x=0.00–0.40; y=0.00–0.32) were prepared by solid‐state reaction route. XRD patterns reveals that there is a single magnetoplumbite phase in the hexaferrites with the substitutiom of Sm (0.00≤x≤0.20) and CrAl (0.00≤y≤0.16) contents, while for the hexaferrites containing Sm (x≥0.30) and CrAl (y≥0.24), impurity phase is detected in the structure. The remanence (Br) decreases with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). With the increase of substitution contents, the intrinsic coercivity (Hcj) increases, while the magnetic induction coercivity (Hcb) first increases, and then decreases. Br has a linear decreasing behavior with increasing temperature from 20 °C to 170 °C. Hcj raises linearly with increasing temperature from 20 °C to 170 °C. The average temperature coefficient of Br (αBr) basically remains constant with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). The average temperature coefficient of Hcj (αHcj) decreases with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). The electrical resitivity (ρ) decreases with increasing substitution content of Sm‐CrAl.

New high-entropy oxide phases with the magnetoplumbite structure

In the studied BaO–SrO–CaO–La2O3–Fe2O3–TiO2–Al2O3–Mn2O3–CoO–In2O3–Ga2O3–Cr2O3 system there were synthesized three new high-entropy magnetoplumbite phases by solid-state sintering in air at 1300, 1350, and 1400 °C.The average composition of the high-entropy phases obtained at 1350 °C can be described by the formulas:Ba0.48Sr0.30Ca0.05La0.15Fe1.62Ti1.78Al1.55Mn1.45Co1.11In1.29Ga1.52Cr1.71O19;Ba0.39Sr0.37Ca0.05La0.18Fe2.88Ti1.60Al1.69Mn1.09Co0.92In1.20Ga1.27Cr1.38O19;Ba0.37Sr0.29Ca0.05La0.28Fe5.85Ti1.15Al0.97Mn0.74Co0.56In0.85Ga0.94Cr0.97O19.The data obtained indicate that a significant portion of calcium was not incorporated into the high-entropy phase. This must be taken into account in the course of subsequent experimental work on the creation of homogeneous phases necessary for the study of their electrical and magnetic properties.

Development of doped Ba–Sr hexagonal ferrites for microwave absorber applications: Structural characterization, tunable thickness, absorption peaks and electromagnetic parameters

In this work, we report microwave absorption characteristics of Ba0·5Sr0·5(CoCr)xFe(12-2x)O19 hexaferrite prepared by a two route ceramic technique. The effect of Co2+-Cr3+content on structural, complex permittivity/permeability and reflection loss properties in Ba0·5Sr0·5Fe12O19 ferrite has been studied. X-ray diffraction confirmed the magnetoplumbite phase in the compositions. The dual absorption peaks were revealed in x = 0.8 composition with reflection loss of −52.09 dB at 8.78 GHz and 5.6 mm thickness. The absorption peaks were found to shift to low frequency with an increase in thickness. Composition x = 0.6 displayed the bandwidth to thickness ratio of 6.5 and a percentage bandwidth of 32.37% at 1.7 mm thickness and 10.13 GHz. The doping of Co2+ and Cr3+ reduced thickness, increased absorption, and bandwidth which is attributed to electromagnetic parameters, input impedance, quarter wavelength theory, and eddy current loss. The investigated performance parameters of prepared compositions indicate good scope for absorber applications.

Preparation and characterization of lanthanum hexa aluminate powders for high temperature applications

In this present study lanthanum hexa aluminate powder was prepared by using chemical precipitation and filtration technique. Powder sample is characterized in terms of composition, morphology, structure, particle size and using complementary techniques such as X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM). It has been observed that the developed powder will have a hexagonal structure with magneto plumbite phase and the particles were obtained have an average grain size of 75 nm.

Structural and Optical Properties of Ba0.7Dy0.3Fe11.4Cr0.6O19/Polyaniline (PANI) Nanocomposites for Optoelectronics

M-type hexaferrites have found considerable application in microwave absorption and magnetic recording. Sol-gel auto-combustion technique was utilized to prepare Ba0.7Dy0.3Fe11.4Cr0.6O19 nano-sized particles which were sintered at 1000 °C for 6 hours. XRD patterns of the prepared sample show magnetoplumbite phase of M-type hexaferrite along with the presence of hematite (α-Fe2O3) and polyaniline. Two specific bands in the range 400-600 cm−1 were observed in the FTIR spectra signifying the formation of hexaferrites structure. The peaks corresponding to polyaniline are also present in the FTIR spectra in the range 800-1600 cm−1. FESEM analysis shows grains with shape similar to hexagonal plate embedded on the surface of polyaniline. The band gap was found to decrease from 1.96 eV to 1.59 eV.

The new extremely substituted high entropy (Ba,Sr,Ca,La)Fe6-x(Al,Ti,Cr,Ga,In,Cu,W)xO19 microcrystals with magnetoplumbite structure

The high entropy oxide phase formation was investigated during solid state sintering at 1300–1350 °C in the BaO–SrO–CaO–La2O3–Fe2O3–Al2O3–TiO2–Cr2O3–Ga2O3–In2O3–CuO and BaO–SrO–CaO–La2O3–Fe2O3–Al2O3–Cr2O3–CoO-Ga2O3–In2O3-WO3 systems. The BaO–Fe2O3–Al2O3–TiO2–Cr2O3–Ga2O3–In2O3–CuO system was proved to form the single phase material with magnetoplumbite structure, which composition was represented by the formula Ba1.00Fe5.83Al1.19Ti1.08Cr1.12Cu0.78Ga1.03In0.97O19. Large configurational entropy of mixing of that phase resulted in significant incorporation of copper, known for its low solubility in the ternary Ba(Fe12-xCux)O19 phase. The structure parameters and magnetic properties of the single phase material were investigated. The Curie temperature of it was as low as 180.4 K due to dilution of high magnetic moment cations with zero magnetic moment cations. Nevertheless, the high concentration of high spin cations ensured enhanced paramagnetic properties of the material.In contrast to the first system, the BaO–SrO–CaO–La2O3–Fe2O3–Al2O3–Cr2O3–CoO-Ga2O3–In2O3-WO3 system formed two phases: the multicomponent spinel phase with low barium, strontium, calcium, lanthanum, and tungsten content along with the multicomponent (Ba, Sr, Ca, La) tungstate phase. High Gibbs energy of formation of the latter phase was the main obstacle for the high entropy magnetoplumbite phase formation.

Effects of Pr-Al co-substitution on the magnetic and structural properties of M-type Ca-Sr hexaferrites

In this research, a series of Pr-Al co-substituted M-type hexaferrites with the chemical composition of Ca0.4Sr0.6-xPrxFe12.0-yAlyO19 (0.00 ≤ x ≤ 0.40, 0.00 ≤ y ≤ 0.60) were synthesized by the standard ceramic method. The phase identification of the samples was confirmed by X-ray diffraction analysis. A single magnetoplumbite phase is exhibited in the hexaferrites with the substitutiom of Pr (0.00 ≤ x ≤ 0.32) and Al (0.00 ≤ y ≤ 0.48) contents. For the hexaferrite containing Pr (x = 0.40) and Al (y = 0.60), an impurity phase α-Fe2O3 is observed in the structure. The morphology of the hexaferrites was analyzed by field emission scanning electron microscopy (FE-SEM). FE-SEM micrographs show that the hexaferrites with different Pr-Al contents have formed hexagonal structures, and the grain size of the magnets decreases with increasing Pr-Al content. A magnetic property measurement system was used to measure the magnetic properties of the hexaferrites. The remanence (Br) and maximum energy product [(BH)max] decrease with increasing Pr-Al content (0.00 ≤ x ≤ 0.40, (0.00 ≤ y ≤ 0.60). The intrinsic coercivity (Hcj) increases with increasing Pr-Al content (0.00 ≤ x ≤ 0.40, (0.00 ≤ y ≤ 0.60). The magnetic induction coercivity (Hcb) and Hk/Hcj ratio first increase with increasing Pr-Al content (0.00 ≤ x ≤ 0.24, 0.00 ≤ y ≤ 0.36) and then decrease with increasing Pr-Al content (0.24 ≤ x ≤ 0.40, 0.36 ≤ y ≤ 0.60).

Investigation on magnetic power loss in strontium doped Ba1-xSrxTi1.2Co1.2Fe9.6O19 hexaferrites

In order to tune magnetocrystalline anisotropy to investigate the influence of anisotropy on magnetic power loss, strontium is added to the BaTi1.2Co1.2Fe9.6O19 ferrite. In the present work, Ba1-xSrxTi1.2Co1.2Fe9.6O19-σ (x = 0,0.1,0.2,0.3) hexagonal ferrites were prepared by solid state reaction method. XRD, SEM and a BH analyzer were utilized to investigate their structural, morphological and magnetic properties, respectively. The XRD patterns showed that only the magnetoplumbite phase was detected in the sample. The SEM images revealed that the crystal grains are hexagonal flakelets with average ab plane size about 2 μm. Magnetic data analysis indicated that the hysteresis loss increased with strontium doping, but the eddy current loss has smaller at about x = 0.1, which is also evidenced by the loss separation ratio results. Q-factor measurement indicated that strontium doping in hexaferrites can decrease magnetic loss when ferrites store the same magnetic energy.

Crystal structure and magnetic properties of Gd–Cu substituted M-type Sr-hexaferrites synthesized by the co-precipitation method

The hexagonal strontium ferrites doped with diverse molar ratio of gadolinium and copper (Sr1−xGdxFe12−xCuxO19, x = 0.00, 0.05, 0.10, 0.15 and 0.20) were prepared by the co-precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were employed to analyze the phase structure, morphology and magnetic performance, respectively. The samples with x from 0.00 to 0.10 were confirmed to a single magnetoplumbite phase, and the impurity phases were detected when the content of dopants x ≥ 0.15. The surface morphology of Sr1−xGdxFe12−xCuxO19 presented hexagonal shape and revealed average grain size increased with the increasing Gd–Cu substitution amount. With the increase of doping amount x, the saturation magnetization (Ms), remanent magnetism (Mr) and coercivity (Hc) firstly increase, and then decrease. When x was 0.10, the Hc arrived at 7203.42 Oe.