M-type Hexagonal Ferrites Research Articles

Flash combustion prepared Sm and Co doped Sr hexaferrite for environmental applications

Nanotechnology is offering solutions to water contamination issues, as new techniques are needed to improve the removal of harmful compounds from water bodies. Despite previous reviews on this topic, nanotechnology is paving the way for more effective water treatment methods. Understanding the substitute influence of divalent Co2+ and rare earth elements Sm3+ on the structure, magnetic, and removal efficiency of hexagonal ferrites requires an understanding of a sequence of SrFe12O19, SrFe11.5Co0.5O19, Sr0.95Sm0.05Fe12O19, and Sr0.95Sm0.05Fe11.5Co0.5O19 M-type hexagonal ferrites were prepared using the flash technique. The XRD examination revealed that the crystallized material formed a single M-type hexagonal phase. The characteristics of M-type hexagonal ferrites include absorption bands with low wavenumbers in the FTIR curves between 400 to 1000 cm−1. There was a variation in magnetic characteristics with the replacement of Sm3+ and Co2+ doping, possibly due to the spin canting impact created by rare earth Sm3+ and Co2+ ions. The goal of the research is to explore the potential of doping magnetic hexaferrites and its influence in wastewater treatment. Various parameters, such as pH and contact duration, that influence the adsorption of lead ions from aqueous solutions were also examined. At pH 7 and 25 °C after 70min, the maximal removal efficiency of the Sr0.95Sm0.05Fe11.5Co0.5O19 was found to be 99%. Magnetic separation was carried out by applying an external magnetic field using a permanent magnet. The strong magnetization of the ferrites (51–58 emu/g) enabled the rapid separation of the magnetic particles from the solution, with over 95% of the ferrite particles being recovered within 10 to 70 min. The Freundlich isotherm model fitted all the isotherm data. Adsorption kinetics were explained by the pseudo-first-order, pseudo-second order, and intraparticle diffusion models. The investigated samples’ adsorption capacity remained efficient till 5 cycles.

Structural elucidation, morphological properties, dielectric properties and their physical interpretation of cerium-substituted cobalt and barium-based M-type hexagonal nano ferrites

This research uses the sol–gel method to look into how adding Co2+ and Ce3+ dopant cations changes the structure, shape, and electrical properties of M-type Ba hexagonal ferrites that have been synthesized. x-ray diffraction (XRD) analysis confirms the successful formation of the targeted hexagonal M-type crystal structure. We observed a reduction in unit cell volume and lattice parameters as the dopant concentration increased, indicating the effective incorporation of dopant ions into the crystal lattice. When the doping process happened, needle-like grain shapes appeared, which could be seen with a field emission scanning electron microscope (FESEM). As the concentration of the dopant increased, the dielectric spectroscopic measurements revealed an increase in the loss tangent (tan δ) from 0.05 to 3.68, and a decrease in the dielectric constant (ε′) from 283 to 3.41. This suggests a reduction in polarization and dielectric permittivity, as well as increased energy dissipation within the material. The electric modulus spectra showed relaxation behaviour that was non-Debye-type, which is another sign that there are complex and multifaceted ways for charges to move. The measurements of relaxation time and AC conductivity showed that the relaxation intervals were not regular and that the conductivity dropped from 2.22*10–4 Ω−1m−1 to 1.4*10–7 Ω−1m−1 as the doping concentration increased. Based on these findings, it seems that the processes of conductivity and dielectric relaxation play a big role in how charges move around in the doped ferrites. We validated complex impedance data obtained through electrochemical impedance spectroscopy (EIS) software against calculated impedance values. The derived grain and grain boundary characteristics also agreed with the observed grain distribution and boundaries from the micrographs, further corroborating the analysis.

Investigating grain and grain boundary effects on charge transport and dielectrics in BaCoxAlxFe12-2xO19 nanoferrites

This investigation centres on the sol-gel preparation of M-type barium hexagonal ferrite (M-BaFe12O19) incorporating Co2+ and Al3+ as dopants. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were employed to assess the impact of dopants on the crystallographic structure and microstructure. The dielectric characteristics, electric modulus, impedance, and conductivity of the synthesized materials were evaluated at ambient temperature using an impedance analyzer. The structural analysis verified the presence of the hexagonal M-type crystal phase. Increasing dopant levels led to a reduction in lattice parameters, signifying unit cell shrinkage. FESEM imaging exposed the emergence of needle-shaped grains resulting from the doping process. Dielectric spectroscopy showed a decrease in both the dielectric constant (from 135.95 at x = 0.0 to 39.8) and the loss tangent (from 3.68 to 0.610) as dopant concentration increased. Conductivity exhibited relaxation at varying intervals, supported by the electric modulus spectra, which validated non-Debye relaxation behavior. Both relaxation time and AC conductivity diminished with higher dopant concentrations (from 0.000222 Ωm−1 to 0.000036 Ωm−1). The relaxation observed in conductivity and dielectric responses implies their contribution to the charge transport processes within BaCoxAlxFe12-2xO19. Electrochemical impedance spectroscopy (EIS) software was used to generate complex impedance plots, which aligned with the experimentally obtained impedance values for the synthesized compositions. Micrographs revealed a distribution of grains and grain boundaries that were consistent with calculated characteristics. This further substantiates the measured dielectric and electrical parameters.

Hexagonal ferrites for self-biasing circulators integrated in LTCC microwave modules

Next-generation microwave LTCC modules for satellite communication systems require the integration of passive components including circulators to manipulate electromagnetic signals at high frequency. Substituted M-type hexagonal ferrites (Ba/Sr)ScxFe12−xO19 are applied as self-biasing microwave magnetic materials at frequencies of about 30 GHz. The ferrites are integrated into LTCC multilayer devices as sintered drop-in bulk samples. Sintered ferrites with preferential orientation of grains were fabricated by compaction of powders in a magnetic field and sintering at 1300 °C. Alternatively, screen-printed ferrite films were dried in an external magnetic field, and cofired at 900 °C. The magnetic texture of the ferrites is characterized using XRD, EBSD, and magnetic measurements. Integrated Y-type circulators were tested and exhibit non-reciprocal behavior. This indicates that hexagonal ferrites are promising candidates for self-biasing circulators embedded in LTCC microwave modules operating at Ka-band frequencies at around 30 GHz.

Influence of bismuth and cobalt doping on structural, dielectric, and magnetic properties of M-type calcium hexagonal ferrites

M-type hexagonal ferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized M-type hexagonal ferrites is still a big challenge. Herein the fabrication of M-type hexaferrite with nominal composition Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with high quality is reported by the sol-gel auto combustion route. The objective of the study is to improve the structural, spectral, dielectric, and magnetic characteristics of M-type hexagonal ferrite which was achieved through the variation of concentration of Cobalt and Bismuth. X-ray diffraction (XRD) patterns confirmed the single-phase M-type hexagonal structure. The crystallite size of all samples was found to be in the range of 42–49 nm. Other parameters such as lattice parameters a & c, unit cell volume, crystallite size, X-ray density, Bulk density, and porosity were also calculated. The doping contents were found to decrease the bulk and X-ray densities while increasing the porosity. Fourier-transform infrared (FTIR) spectra showed the formation of metal-oxygen stretching vibrations that confirmed the formation of hexagonal ferrites. The scanning electron microscopy (SEM) images revealed a regular platelet hexagonal structure and homogeneously distributed grains were examined. The dielectric constant was high at low frequency and then decreased with increasing frequency, while the dielectric loss was decreased appreciably with doping. The saturation magnetization ranged from 15.51 to 38.27 emu/g, coercivity increased from 207.93 to 1359.69 Oe, and the squareness ratio was found to be in the range of 0.19–0.78. The dielectric and magnetic properties of Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with the variation of Co and Bi revealed that these materials are good candidates for modern devices.

Structural, morphological, and EMI shielding evaluations of Sm-Mn co-doped Sr-based M-type hexaferrite for Ku band applications

High-performance, thin, and lightweight EMI (Electromagnetic interference) materials with outstanding shielding effectiveness were explored over the last years to solve the problems in electronic devices. Magnetic absorbing materials have extensive bandwidth, good impedance matching, and excellent absorption features. In the present study, Sm-Mn Sr-doped M hexaferrites with Sr1-xSmxFe12-yMnyO19 whereas (x= 0.00, 0.025, 0.05, 0.075, y = 0.00, 0.25, 0.5, 0.75) were prepared by the chemical route. XRD, FESEM, HRTEM, FTIR, VSM, and VNA are used to evaluate the properties of the Sm-Mn doped Sr-based M-type hexagonal ferrite. The XRD (X-ray diffraction) results revealed the presence of a hexagonal phase in the prepared samples. Rietveld refinement also confirmed the phase purity for the Sm-Mn doped Sr-based M-type hexagonal ferrites. The FESEM (Field emission scanning electron microscopy) and HRTEM (High-resolution transmission electron microscopy) images revealed the hexagon-type shapes of the particles in the Sm-Mn doped Sr-based M-type hexagonal ferrites. The FTIR (Fourier transform infrared spectroscopy) spectra showed the 446–620 cm-1 lines, confirming the presence of the tetrahedral and octahedral phases of hexagonal ferrites. Dielectric and electromagnetic shielding effectiveness (SE) parameters are evaluated for Sm-Mn doped Sr-based M-type hexagonal ferrite. The electromagnetic parameters, such as complex refractive index, absorption and impedance, are also investigated for the Sm-Mn doped Sr-based hexagonal ferrite powder with x=0.075, y=0.75 having epoxy resin with 20 wt%, 30 wt% and 50 wt% samples, respectively. SE parameters are higher at more extensive filler loading. The green shielding index was found higher for Sm-Mn doped Sr-based hexagonal ferrite powder with x=0.075, y=0.75 having 20 wt% epoxy resin and decreased with filler loading. It is found the epoxy/Sm-Mn doped Sr-based M-type hexagonal ferrites-based composites are excellent absorbers in the Ku band. The investigated absorbers could be the best candidates for next-generation EMI green shielding absorbing devices and applications.

Facile synthesis of novel hexagonal strontium ferrites for promising adsorption of cadmium from aqueous solutions

Cadmium (Cd(II)) contamination in both the surface and ground water is threatening the lives of millions of people across the world. In this work, we have hydrothermally synthesized the novel multiphase (MP) and single phase (SP) M-type hexagonal strontium ferrites (SF, SrFe12O19) for removing Cd(II) from contaminated water. The as-synthesized materials were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectrometry (XPS). The MP-SF and SP-SF demonstrated excellent Cd(II) adsorption capacities over wide pH range. The pseudo-first and second-order kinetics models as well as the Langmuir and Freundlich isotherms models were used for fitting the experimental data for adsorption of Cd(II) on both the MP-SF and SP-SF. The maximum adsorption capacities reached to 57.5 and 78.9 mg/g for the MP-SF and SP-SF, respectively, at pH 7, which were better than many recently reported magnetic adsorbents. The effects of common co-existing ions on the adsorption capacities of both the MP-SF and SP-SF were also evaluated. FTIR and XPS spectroscopic analyses further confirmed that Cd(II) was adsorbed on to the surface of SP-SF through the formation of an inner-sphere complex between the Cd(II) and surface metal centers.Furthermore, the as-synthesized materials were employed for the treatment of simulated real Cd(II) contaminated water. The experimental results suggested that the SP-SF could be a strong candidate for practical applications of Cd(II) removal from aqueous solutions.

Machine learning prediction and experimental validation of magnetic properties of M-type hexagonal ferrites

M-type hexagonal ferrites have received widespread attention for their excellent magnetic properties, but studying the intricate interplay between their composition, process and magnetic properties has long been a puzzling task. The advent of machine learning offers a promising example for accelerating the discovery of connections between them. In this work, we trained five machine learning regression models (SVR, DTR, AdaBoost, GBDT and MLP) using data collected from the literature and found that the SVR model performed well on the dataset. In order to verify the feasibility of the SVR model, we predicted the magnetic properties of Ba1-xLaxFe12-yMnyO19 (0.1≤x=y≤0.6), and then prepared and tested them. The results showed a good agreement between the prediction and the experiment, which proved the reliability of the designed model. Moreover, we elucidate the occupancy trend of Mn3+ ions by first principles calculation and Raman spectroscopy verification. This work strongly suggests that machine learning has the potential to explore the relationship between composition, process and properties, which opens the door for the tailoring the properties of M-type hexagonal ferrites.

Tailoring permittivity and permeability of M-type hexagonal ferrite and 2D Ti3C2Tx MXene composites for broadband microwave stealth performance

In this study, owing to the significant advantages of heterogeneous interface engineering for customizing the electromagnetic parameters and microwave absorption properties, high magnetic lossy cobalt/zinc-doped hexagonal ferrite flakes were successfully anchored on two dimensional Ti3C2Tx with varying mass ratios. Inorganic Ti3C2Tx MXene was synthesized through the hydrofluoric acid etching process, and doped hexagonal ferrite was prepared by a solid-state sintering route leading to electrostatic bonding with Ti3C2Tx particles. Scanning electron microscopy revealed that the MXene surface strongly adhered to the ferrite particles. By adjusting the ratio of ferrite to Ti3C2Tx, it is feasible to optimize electromagnetic parameters, as required. Specifically, doped ferrite@4% Ti3C2Tx MXene composite exhibited remarkable absorption performance; the maximum reflection loss (RL) was −49 dB at 15.2 GHz with a thickness of 1.9 mm. The effective bandwidth corresponding to the RL values below −10 dB is 8.3 GHz (from 9.7 GHz to 18 GHz) at a single thickness of 2 mm, and below −15 dB is 6.4 GHz (from 10.7 GHz to 17 GHz), outlining the prospect for application as an electromagnetic wave absorber. Radar cross-section (RCS) simulation was performed with microwave incident angles ranging from 0 to 360°. The results demonstrate a reduction in RCS of up to −47.8 dBsm at a 60° incident angle. This study develops a new approach for constructing multi-component heterostructure composites with tailored electromagnetic parameters as a superior and modulated radar stealth material.

Influence of La3+-Co2+ substitution on X-band microwave absorption properties of Ba0.5Sr0.5Fe12O19 nanoparticles with insight into quarter wavelength phenomenon

The presented study aims to tune the microwave absorption properties by varying the chemical composition of Ba0.5Sr0.5Fe12O19 nanoparticles with Co–La substitution via the synthesis route of the sol-gel citrate precursor method. X-ray diffractograms (XRD) and Fourier Transformed Infrared Spectroscopy (FTIR) confirmed the formation of pure phase M-type hexagonal ferrite with varying lattice parameters. The permittivity measurements revealed increased dielectric losses, indicating good energy dissipation behavior. Enhancement of magnetic behavior resulted from the strengthened exchange interactions between lattice sites, leading to higher permeability values. Significant reflection losses were exhibited by our synthesized samples with a maximum reflection loss of −42.08 dB at 4.62 GHz for x = 0.35 at an experimental thickness of 3 mm. The dependence of reflection loss peaks on matching thickness was analyzed using calculated thickness profiles, revealing their close agreement with simulated thickness. The study highlighted the potential of synthesized samples for electromagnetic signature reduction, in both commercial and military applications.

Investigation of crystal structure, Raman spectroscopy and magnetic properties of La-Zn substituted oriented M-type hexagonal barium ferrites

M-type hexagonal barium ferrite (BaM) has received much attention in the application of self-biased microwave devices because of its large anisotropic field (Ha) and high saturation magnetization (Ms), but the increased Ha inevitably increases the microwave magnetic loss of the device. In addition, the devices need to have a high Ms for high frequency applications. To address these issues, we used La3+ and Zn2+ instead of Ba2+ and Fe3+ ions to modulate the Ha and Ms of BaM, respectively. Ba1-yLayFe12-xZnxO19 (x=y=0.1–0.5) M-type hexagonal ferrite was synthesised by conventional solid-phase methods. The La-Zn co-substituted BaM samples were shown to be purely single phase by X-ray diffraction (XRD) analysis. The lattice parameters, specific surface area, crystallite size, dislocation density and microstrain of the samples were also calculated using the XRD data. Furthermore, La3+ and Zn2+ can not only modulate the sample Ha and Ms between 10,214–12,102 Oe and 62.94–78.23 emu/g, respectively, while making the sample more denser. At x=0.3 BaM detects relatively satisfactory properties: large Ms=63.12 emu/g, suitable Ha=10,214 Oe and Hc=2248.87 Oe, high Mr/Ms=0.832 and narrow ferromagnetic resonance linewidth (= 903 Oe), which provide good candidates for next-generation self-biased and low-loss microwave wave devices.

Improvement in the structural, magnetic and electromagnetic behaviour of barium hexaferrites with yttrium doping for EMI shielding

Electromagnetic interference (EMI) shielding is critical for protecting electronic devices from interference generated by various sources such as power lines, radio waves, microwaves, and electronic devices. In this current study, we present a thorough investigation of the structural, magnetic, and electromagnetic properties of Y3+ doped M-type barium nano hexaferrites. Polycrystalline BaFe12−xYxO19 (x = 0.0, 0.3, 0.5, 0.7, and 0.9) hexaferrites are prepared using the citrate precursor method. The results of X-ray diffraction (XRD), Rietveld refinement and Raman spectroscopy confirmed that all samples have a single-phase, and pure hexagonal crystalline structure with space group P69/mmc. This result is consistent for all the prepared compositions. The structure and dopant materials in different chemical states of the sample are determined based on the X-ray photoelectron spectroscopy (XPS) spectrum. Field emission scanning electron microscopy (FESEM) analysis showed that the particles had a distinct hexagonal morphology. The chemical composition of the prepared hexaferrites is investigated using energy dispersive X-ray analysis (EDAX). UV spectroscopy showed an inverse relationship between the molar ratio of yttrium and the band gap. Vibrating sample magnetometer (VSM) results showed a decrease in saturation magnetization (Ms) and coercivity (Hc) with increasing fraction of yttrium ions. The shielding efficiency (SE) of the synthesized hexa materials against EMI is evaluated using a vector network analyser (VNA). In particular, effective EMI shielding was observed in the frequency spectra of 8–12 GHz (X-band region). Among the tested compositions, BaFe12–0.7Y0.7O19 with a thickness of 3 mm exhibited highest SE of 80.07 dB in the X-band region. The proposed yttrium-substituted barium M-type hexagonal ferrites exhibit significant reflection loss with enhanced absorption spectrum even when applied to an extremely thin 3 mm material, making it a possible preference as the radar-absorbed compound for EMI attenuators for weather monitoring, radar tracking, air traffic management, and gigahertz antennas. Furthermore, commercial applications including long-term magnetic media for recording, storing information, etc. are possible uses of the synthesised magnetic yttrium-doped barium M-type hexagonal ferrites.

Magnetic Properties of M-Type Hexagonal Ferrite: Mechanical Applications

As the information era continues to advance at a rapid pace, M-type strontium ferrite and other magnetic materials are finding more and more traditional uses. Numerous industries rely on it as a permanent magnet material because of its inexpensive cost, ease of preparation, and outstanding overall performance in areas including electronics, national defense, and communication. In this paper, we investigate some the magnetoelectric coupling properties at room temperature by solid phase method and sol-gel method. The phase structure was determined using an X-ray diffractometer, and the samples were all single-phase polycrystalline with a spatial group of P63/mmc. Observing the surface morphology using field emission scanning electron microscopy, it was found that the composition distribution of the samples prepared by solid-phase method was uneven and there was a "scandium rich phase". The samples prepared by the sol gel method have uniform composition distribution, hexagonal grain shape, and grain size of about 3-5 μ M. The magnetic properties of the samples prepared by the sol gel method and the solid phase method were studied, respectively. The results showed that the phase transition occurred in the solid phase method at about 250K, and the hysteresis loop at room temperature did not show the magnetoelectric coupling behavior. The magnetic phase transition of the sample prepared by the sol gel method occurred near 330K. Combined with the research on the hysteresis loops of the temperature above and below this phase transition point, it shows that this phase transition corresponds to the change of the ferromagnetic to the conical magnetic structure. The similar relationship between magnetic capacitance and magnetization intensity with magnetic field indicates that this conical magnetic structure can induce ferroelectric polarization, which can be understood based on the inverse Dzyaloshinskii-Moriya model.

Optical, dielectric and photocatalytic properties of Ag-doped Sr1−xAgxFe12O19 and CV dye degradation under visible light irradiation

In the present study, a series of silver-doped strontium hexaferrite (Sr1−xAgxFe12O19) were fabricated by microemulsion route. The influence of dopant (Ag) on the structural, dielectric, optical and photocatalytic properties was analyzed, which were characterized by XRD, Raman, SEM, FTIR and UV–visible techniques along with photoluminescence and dielectric measurements. The XRD and Raman studies display the M-type hexagonal ferrite formation with a P63/mmc space group with an average crystallite size of 25–32 nm. For Ag-doped SrFe12O19, the UV–visible absorption coefficient showed a substantial red shift, leading to the reduction of the bandgap to 3.2–2.6 eV. The PL spectra reveal that highly doped materials displayed lower re-combination and enhanced charge-separation (e--h+). With dopant concentration, the dielectric loss decreased, while AC conductivity and dielectric constant increased. The photocatalytic activity was studied by degradation of the crystal violet (CV) dye under visible light irradiation and up to 86% dye degradation was achieved for Sr1−xAgxFe12O19 versus SrFe12O19 (54%) in 120 min. Moreover, the stability was confirmed by consecutive cycles and doped material showed higher stability and reusability versus undoped. The effect of different scavengers was also studied to evaluate the dye degradation mechanism. In view of enhanced optical and catalytic properties, the Sr1−xAgxFe12O19 could be employed for the remediation of dyes in textile effluents under solar light irradiation, which will make the process economical versus UV light-based photocatalytic processes.

Optical spectroscopic analysis, supercapacitance, photocatalysis of BaTixFe12-(4/3)xO19 hexagonal nanoparticles

Obviously, BaTixFe12-(4/3)xO19 Hexagonal nanocrystals are excellent candidates as photocatalysts in water purification, as well as using them as electrode materials for supercapacitors and energy storage applications. M-Type Hexagonal nanoparticles (BaTixFe12-(4/3)xO19, 0 ≤ x ≤ 1) with the magneto-plumbite structure were formerly synthesized by co-precipitation procedure and investigated by several techniques such as XRD, FT-IR, Raman, Photoluminescence and UV-VL. XRD and FT-IR confirmed the structure, and Raman spectra showed 12 characterizing summits. Photoluminescence emission spectra indicated two summits at 448 and 501 nm. Optical UV-VL spectroscopic analysis parameters showed dependence on λ and x. Obviously, BaTi0.75Fe11O19 nanocrystals as a sort of M-Type Hexagonal Ferrites showed excellent Photocatalytic activity on the Degradation of Organic Dyes like; Crystal Violet, Methyl Orange, … etc. Furthermore; these nanocrystals possess excellent electrochemical performance; which in turn introduces these materials for Supercapacitors Applications. Thus, the Photo-catalytic activity of BaTi0.75Fe11O19 nanocrystals for the decolorization of Crystal Violet (CV) dye (1 × 10-5 M) illuminated excellent photocatalytic efficiency reaching ≈ 85%. On the other hand; BaTi0.75Fe11O19 nanoparticles exhibited a specific capacitance of 1858 mF/g at 50 mV/s. The current study introduces promising applications of BaTi0.75Fe11O19 nanoparticles as electrode materials for super capacitance and energy storage.

Structural and magnetic properties of BaFe9.95Al2Mg0.05O19 tuned through sintering temperature

The sintering temperature is a key way to tune the structural and magnetic properties of M-type hexaferrites. Here the effect of BaFe9.95Al2Mg0.05O19 M-type hexagonal Ba-hexaferrites, was studied. X-ray diffraction analysis revealed the presence of Fe2O3 impurity phases in all samples. The results showed that as the sintering temperature increased, the saturation magnetization (Ms) and remanence ratio (Mr/Ms) initially increased, then decreased at higher temperatures. On the other hand, the coercivity (Hc) and magnetocrystalline anisotropy field (Ha) decreased first, then increased. The average grain size (D) consistently grew between 800–2800 nm with increase in pre-sintering temperature. The optimal magnetic properties of BaFe9.95Al2Mg0.05O19 were achieved at a pre-sintering temperature of 1280 °C, with Ms = 49.94 emu g−1, Hc = 4.99 kOe, Ha = 1.5 kOe, and mB = 9.4097 μB. The findings suggest that magnetic properties of M-type hexagonal strontium ferrite can be significantly enhanced by optimizing the pre-sintering temperature, which has implications for the development of high-performance self-biased circulators, Magnetic filters and other magnetic applications.

Structure and magnetic properties of Al3+ substituted M-type SrLaCo hexaferrite

M-type hexagonal ferrites (SrFe12O19) have attracted much attention as a widely used permanent magnet. Many studies have been done to improve permanent magnetic properties. In particular, the formula of La–Co co-replaced Sr–Fe has achieved higher performance. However, no one has studied the influence of a small amount of Al ions on the above formula. In this study, the Al3+ ion substituted M-type Sr0.7La0.3Fe11.75ￚxAlxCo0.25O19 (0 ​≤ ​x ​≤ ​0.12) hexagonal ferrites were synthesized by solid state reaction. The crystalline structure was investigated by using X-ray diffraction (XRD) and the Rietveld refining method. The morphological of powder and magnetically oriented bulk were observed by scanning electron microscopy (SEM), and magnetic properties were measured by physical property measurement system-vibrating sample magnetometer (PPMS-VSM) techniques. The results show that a single M-type strontium ferrite was obtained with the Aluminum (Al) content (x) from 0 to 0.08, and the impure phase appeared when x was 0.12. The lattice parameters a and c both decreased with the increasing Al3+ content. SEM images indicate the hexagonal platelet-like particles and the size of the magnetic powders about 2–5 ​μm, and the powders are easily arranged in one direction under a magnetic field. The saturation magnetization (Ms) of the hexaferrite decreased with the increase of x from 0 to 0.12, but coercivity (Hc) of the magnetic powders increased with Al3+ content (x) from 0 to 0.12.

Crystal structure and magnetic properties of Ga-Mn cosubstituted M-type strontium ferrite synthesized by sol-gel method

The M-type hexagonal strontium ferrites substituted by Gd-Mn ions were synthesized by the sol-gel self-combustion method. The synthesized samples were researched by X-ray diffraction (XRD), Fourier transform infrared spectroscopy analysis (FT-IR), scanning electric microscopy (SEM), and vibrating sample magnetometer (VSM). The XRD and the FT-IR results show that the pure M-type hexagonal ferrites phase is successfully obtained in the samples with the substitution amount (x) from 0.00 to 0.09 of Gd-Mn. The VSM results show that, as the substitution amount (x) of Gd-Mn increases, the remanent magnetization (Mr) and saturation magnetization (Ms) of the Sr1-xGdxFe12-xMnxO19 gradually increase, and the maximum values of 39.53 emu/g and 23.73 emu/g were obtained when x = 0.09. When x continues to increase, Mr and Ms decrease slightly, but they are still higher compared with those of the unsubstituted one. The coercivity (Hc) of the samples after doping is much higher than the coercivity of the pure sample, but as the substitution amount x increases, the coercivity first increases and then decreases, while the maximum value of Hc is 6738 Oe at x = 0.06.

Investigation of BaFe12O19 Hexaferrites Manufactured by Various Synthesis Methods Using a Developed Pulsed Magnetometer

The manufacture and study of the properties of magnetic materials requires the development of new automated devices for measuring their magnetic properties. To obtain nanosized materials with a pure phase, it is necessary to modernize former methods and develop new methods for synthesizing materials. As part of this study, a pulse magnetometer was made to study magnetic hysteresis loops. An exceptional feature of this device is the ability to conduct studies of the full cycle of the hysteresis loop using pulsed magnetic fields. M-type BaFe12O19 hexagonal ferrites were synthesized by standard ceramic, mechanochemical, and sol–gel methods. The structural, phase, and magnetic characteristics of the barium hexaferrites were studied. Methods for the synthesis of BaFe12O19 hexagonal ferrites were estimated and compared. Their structural and magnetic properties essentially depend on the method of synthesis. The mechanochemical technology makes it possible to obtain materials without impurity phases through the use of hydrated reagents in the synthesis. The use of sol–gel technology allows the synthesis to be carried out at much lower temperatures.

Enhanced magnetic properties of Sr0.7Ce0.3Fe11.7Zn0.3O19 by tuning pre-sintering temperature

In this work, pre-sintering temperature was tuned to investigate its effect on the structural and magnetic properties of oriented M-type hexagonal strontium ferrite Sr0.7Ce0.3Fe11.7Zn0.3O19. X-ray diffraction pattern shows that Fe2O3 and CeO2 impurity phases exist in all samples. As pre-sintering temperature increased, both saturation magnetization (Ms) and remanence ratio (Mr/Ms) first increased and then decreased. In contrast, coercivity (Hc) and magnetocrystalline anisotropy field (Ha) first decreased and then increased as pre-sintering temperature went up. The average grain size (D) increases monotonously with pre-sintering temperature. At pre-sintering temperature of 1200 ℃, Sr0.7Ce0.3Fe11.7Zn0.3O19 achieved optimal magnetic properties of Ms = 58.24 emu/g, Mr/Ms = 0.95, Hc= 1816 Oe, Ha= 10433 Oe and K1 = 1.51 × 105 J/m3. This work shows that the magnetic properties of M-type hexagonal strontium ferrite could be significantly improved by optimizing the pre-sintering temperature, which helps the design of high-performance and self-biased circulator.