Barium Ferrite Research Articles

Exquisite regulation of LZ-BaM/PPy composites for compatible absorption across centimeter-wave and millimeter-wave bands

The increasing complexity of the electromagnetic environment necessitates materials to exhibit superior microwave absorption performance for multitudinous bands. However, reaching satisfactory compatibility for absorption across centimeter-wave and millimeter-wave bands still remains a formidable challenge. In this work, a composite composed of Polypyrrole (PPy) and La3+-Zr4+ co-doped barium ferrite (LZ-BaM) is elaborately designed to address the issue facing us today. By exquisitely regulating the chemical composition, absorption peaks ascribed to different integral orders of interference can appear simultaneously in millimeter-wave and centimeter-wave bands. Ultimately, the as-prepared LZ-BaM/PPy composite reveals an efficient absorption (RL < −5 dB, absorptivity of 68.37 %), covering the centimeter-wave band of 8∼17 GHz and millimeter-wave band of 27∼40+ GHz concurrently under a matching thickness of 2.4 mm. This study thus offers valuable insights for the development of high-efficient absorbers across multiple frequency bands.

Evaluating the potential white shark (Carcharodon carcharias) swim pattern manipulation capabilities of the novel and noninvasive Shark Exclusion Barrier

Abstract Even though the risk of a negative encounter with a large and potentially dangerous shark species (e.g. white sharks—Carcharodon carcharias) is exceedingly rare, some localities implement indiscriminate shark culls to minimize this risk. Due to the negative ecological impact that these lethal shark control measures can have, the present study aimed to test a novel and eco‐friendly shark barrier system, known as the Shark Exclusion Barrier. The Shark Exclusion Barrier is a shark deterrent technology that is composed of a combination of interconnected and telescoping vertical barrier elements (i.e. the visual stimulus) and electromagnetic stimuli (e.g. electromagnets and Barium Ferrite (BaFe12O19) permanent magnets). Using this system, two separate C. carcharias swim pattern manipulation studies were conducted over the course of two research seasons. In the first season (i.e. 2021), 9, 1‐h trials were conducted where 9–13 different C. carcharias interacted with the barrier. In the second season (i.e. 2023), 35, 2‐h trials were conducted where 6–10 C. carcharias interacted with the barrier. Throughout experimentation, C. carcharias exhibited a significantly greater entrance frequency (p &lt; 0.05) and a significantly reduced pass around frequency (p &lt; 0.05) towards the control region when compared to the Shark Exclusion Barrier region. Furthermore, the barrier exhibited the ability to maintain its structural integrity during swells of ≥2.13 m, breaking waves of ≥1.52 m and a current of ≥1.12 m/s. Due to the promising results, this technology warrants further investigation to determine if it is a plausible alternative to lethal culling measures.

Effect of annealing temperature on crystallographic texture, magnetic and microwave properties of barium ferrite thin films

Due to it has large saturation magnetization (Ms), high magnetocrystalline anisotropy field and high ferromagnetic resonance (FMR) frequency, barium ferrite (BaM) has attracted more and more attentions in the fields of magnetic recording media, permanent magnets and microwave devices. Here, BaM thin films were deposited on Pt/TiO2/SiO2/Si substrates, and the effect of annealing temperature on the microstructure, magnetic and microwave properties of barium ferrite thin films was investigated in detail. It is found that when the BaM thin film was annealed at 1035 °C, it has good properties. The XRD data provide clear evidence that the BaM thin films have high c-axis orientation, and the Lotgering factor is as high as 0.96. The AFM morphology show that BaM grains are out of the film plane, and they are hexagonal. The magnetic hysteresis curves indicated that both saturated magnetization (4πMs), remanence ratio and coercive (Hc) for out of plane increase with increasing Ta first, then decreased, and get the maximum value at 1035 °C. The ferromagnetic resonance (FMR) measurement show that the FMR linewidth is 143 Oe@50 GHz, it means that this this sample has low microwave loss in millimeter wave loss, and the FMR absorption can be tuned by applied magnetic field. These results make sure that this BaM thin film is possible use in millimeter wave devices such as filers, circulators and isolators.

Influences of divalent ion substitution on the magnetic and dielectric properties of W-type barium ferrite

Abstract Saturation magnetization, magneto-crystalline anisotropy field and dielectric properties are closely related to microwave devices applied at different frequencies. For regulating the magnetic and dielectric properties of W-type barium ferrites, single-phase BaMe 2Fe16O27 (Me = Fe, Mn, Zn, Ni, Co) with different Me ions were synthesized by the high-temperature solid-state method. The saturation magnetization (M s) range from 47.77 emu/g to 95.34 emu/g and the magnetic anisotropy field (H a) range from 10700.60 Oe to 13739.57 Oe, depending on the type of cation substitution in the hexagonal lattice. The dielectric permittivity and dielectric loss decrease with increasing frequency of the AC electric field in the low-frequency region, while they almost remain constant in the high-frequency region. The characteristics of easy regulation and preparation make it a potential candidate for use in microwave device applications.

Synthesis and Characterization of Barium Hexagonal Ferrite (BaFe12O19)

Barium Ferrites is a good class of electrical material due to its high resistivity. It is mainly used in electronics and telecommunication industry due to their novel electrical properties. We have synthesized barium hexagonal ferrite (BaFe12O19) by solid state reaction method. The prepared precursor was calcined at temperature 750°C and characterized by FTIR, XRD and SEM. X-ray diffraction analysis confirmed the single-phase formation of BaFe12O19. Using the Debye Scherrer formula, the crystallite size of BaFe12O19 was calculated, and the average particle sizes were 26.52 nm, 27.17 nm, 19.17 nm and 23.67 nm. The result confirms that barium ferrite powder has a constant size of less than 30 nm. Four peaks at 2θ values of 35.52, 43.22, 57.21 and 62.84 degrees, corresponding to (110) (111) (210) and (211) planes of Barium ferrite have been observed. The FTIR spectra showed important signature absorption spectra of hexaferrite at 314 cm−1, 499 cm−1 & 628 cm−1. These peaks confirm the formation of barium hexaferrites. The SEM images of barium hexaferrite at 750°C showed large number of vertically grown barium hexaferrite nanorods with a grain size between 110 nm to 130 nm. Thus, barium ferrite is a good candidate in the use of electronics and communication sector.

Barium Ferrite/Carbon Nanotube Nanocomposites for Millimeter‐Wave Electromagnetic Shielding Enhanced by Ferromagnetic Resonance Absorption

In this work, a composite of barium ferrite (BaM) and multiwalled carbon nanotubes (CNTs) in a polymer matrix of polydimethylsiloxane (PDMS) are reported for the purpose of suppressing electromagnetic interference (EMI). Shielding is accomplished primarily through absorption, which arises from a combination of the ferromagnetic resonance (FMR) from the BaM and conductive losses from the CNTs. The composite is fabricated by mixing commercially available BaM nanoparticles and CNTs into PDMS, screen printing the mixture into molds, then curing at 80 °C in a DC magnetic field. Characterization involves placing the composite in the cross‐section of a rectangular waveguide, then using a vector network analyzer (VNA) to measure scattering (S) parameters from 33–50 GHz. Using the measured S parameters, power reflected and absorbed can be calculated and used to characterize the composite's shielding effectiveness (SE), and the complex permittivity and permeability can be determined. The resulting 2.4 mm thick composite shows a peak absorption of 26.9 dB at the FMR frequency of 47.4 GHz. When normalized for thickness, the composite, on average, absorbs 11.3 dB mm−1 and operates at a higher frequency than other shielding composites found in the literature.

Rare earth Ce-doped W-type barium ferrites for tunable electromagnetic waves absorption performance

W-type ferrites possessing low cost and high chemical stability, show high potential in electromagnetic wave (EMW) absorption field. However, due to the low dielectric loss, developing high EMW absorption performance of W-type ferrites remains desired. Here, rare earth (RE) cerium (Ce)-doped W-type barium ferrites (Ba1-yCeyNi2Fe15.4O27, y = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) are prepared by a sol-gel approach. The influences of Ce doping are detailed analyzed. Ce ions with unpaired 4f electrons and strong spin-orbit coupling of angular momentum enhance the dielectric and magnetic properties of ferrites. Ba0.7Ce0.3Ni2Fe15.4O27 achieves the minimum reflection loss (RLmin) value of -52 dB while Ba0.6Ce0.4Ni2Fe15.4O27 showcases the widest effective absorption bandwidth (EAB) of 1.36 GHz associated with the RLmin reaching -38 dB, significantly outperforming the undoped ferrites. This work thus demonstrates a high-efficiency utilization of Ce for enhancing the EMW absorption performance of widely employed W-type barium ferrites, efficiently advancing the application field of RE elements.

Effect of Ce doping on electromagnetic characteristics and absorbing properties of M-type barium ferrite

In this study, Ce3+-doped M-type barium ferrite BaCexFe12-xO19 (x = 0 ∼ 1.2) was prepared by sol-gel method. The effects of Ce3+ doping on the crystal structure, microstructure, electromagnetic properties and absorption properties of M-type barium ferrites were investigated. The results indicate that the crystal structure remains unchanged with the increase of Ce3+ doping. The crystal size of Ce3+ doped barium ferrite is in the micro-meter range, and the grain size remains almost constant with increasing doping. The addition of Ce3+ to the BaFe12O19 samples resulted in significant improvements in their electromagnetic and microwave absorption properties. These improvements were mainly due to the synergistic effect of magnetic and dielectric losses. Among the samples doped with different concentrations of Ce3+, BaCe0.2Fe11.8O19 exhibited the best absorption performance, which has a minimum reflection loss of −58 dB and an effective absorption bandwidth of 9.44 GHz at a matched thickness of 2.3 mm. This study proposes an efficient electromagnetic wave absorber with a wider effective absorption bandwidth.

Investigation effect of Lu-substitution on structural, morphological, magnetic, and dielectric properties of BaM hexaferrite synthesized using a co-precipitation method

In this paper, we synthesized Lu-substituted M-type barium ferrites (BaLuxFe12-xO19, x = 0, 0.2, 0.4, 0.6, 0.8) by chemical co-precipitation using a non-stoichiometric ratio of raw materials. We investigated their structure, XPS, and EDX spectra, morphology, and magnetic and dielectric properties. The XRD patterns showed that the diffraction peaks shifted toward a lower angle and the lattice constant ratio (c/a) was less than 3.98, which was within the allowable range of magneto-plumbite structure. XPS and EDX spectra confirmed the presence of O, Fe, Ba, and Lu elements in the samples. SEM images revealed that the ceramic samples sintered at 1330 °C had a regular and obvious hexagonal structure. Lu substitution promoted grain growth, with an average grain size increase of 163% and a maximum grain size of 21.77 µm. Hysteresis loops indicated the formation of a multi-domain structure in the samples. The coercivity decreased from 2035.82 Oe to 574.84 Oe and the saturation magnetization decreased as well but still exceeded 58 emu/g. The dielectric constants of all the samples were in the order of 103 to 104 and the substitution of Lu significantly increased it to about 16k. The tangent loss could be maintained below 0.5, with a minimum of approximately 0.1. The Lu-substitution barium ferrites with high saturation magnetization, low coercivity, high dielectric constant, and low tangent loss coexistence may be a potential candidate for application in low-frequency wireless communication with miniaturization and multifunction.

The Absorption Performance of Composite Materials Combining with Barium Ferrite and Carbonyl Iron

The Absorption Performance of Composite Materials Combining with Barium Ferrite and Carbonyl Iron

Structure and magnetic properties of M-type barium ferrite co-doped with Sm and Nb prepared by solid-phase sintering

M-type barium ferrite with the formula Ba1−xSmxFe12−yNbyO19 (x = 0.00–0.10, y = 0.00–0.20), which was co-doped with Sm3+ and Nb5+ ions, was synthesized experimentally by a modified solid-phase reaction method. The crystal structure of samples was determined by X-ray diffraction, which confirmed that they were of high purity. The X-ray diffraction data were fitted with a full-spectrum correction using GSAS software. By Fourier transform infrared spectroscopy, the samples were observed to exhibit bands due to tetrahedral and octahedral sites at 598 cm−1 and 445 cm−1, respectively. The samples were examined by field emission scanning electron microscopy, which showed that they partly comprised hexagonal structures but mostly consisted of irregular structures with rounded edges. Characterization of the elemental contents of the samples by energy-dispersive spectroscopy revealed an increase in the contents of Sm and Nb and a decrease in the contents of Ba and Fe. The magnetic properties of the samples were examined using a vibrating sample magnetometer. The results showed that the saturation magnetization and residual magnetization of the samples decreased slightly with an increase in the contents of the dopants. The coercivity reached its maximum value, namely, 3367.53 Oe, when x = 0.04 and y = 0.08.

Modulation effect of Zr-Sm co-doped on microwave absorption performance of barium ferrite

Zr-Sm co-doped barium ferrites BaFe12–2x(ZrSm)xO19(x = 0, 0.2, 0.4, 0.6) were successfully prepared by sol-gel method. The effects of Zr-Sm co-doped on phase formation, microscopic morphology, magnetic parameters, electromagnetic and microwave absorption properties of barium ferrite were studied. The results show that the saturation magnetization(Ms) of BaFe12–2x(ZrSm)xO19 first increases and then decreases, the coercivity(Hc) first decreases and then increases with the increase of doping amount(x) of Zr-Sm. Large grain size and sheet morphology lead to the transition of BaFe11.6(ZrSm)0.2O19 towards soft magnetic properties. The introduction of Zr-Sm increases the amount of oxygen vacancies, and dielectric loss value of material is obviously enhanced, this improves the polarization relaxation of materials. At the same time, multiple natural resonance peaks appeared in the virtual part of the permeability (μ"), which regulated the absorbing properties of samples. The best microwave absorption properties of sample is obtained when doping x = 0.2, at the thickness of 2.8 mm, the maximum reflection loss(RL) is − 51.75 dB. The effective absorption bandwidth (RL ≤ −10 dB) is 4.4 GHz, it covers almost all the X-band(8–12 GHz). Compared with existing doped barium ferrite, the material possesses a greater reflection loss and excellent prospects in the field of microwave absorption.

Achieving Superior Electromagnetic-Absorbing Performances in the Hexagonal Flake BaFe12O19@PVDF Composites.

Combining magnetic and dielectric materials to form a composite can significantly improve its impedance matching and electromagnetic wave absorption performance. Furthermore, composite materials with a core-shell structure hold promise in meeting the demand for lightweight and highly electromagnetic-absorbing properties. In this study, uniform hexagonal flake barium ferrite (BaFe12O19) was prepared using the hydrothermal method. Subsequently, BaFe12O19@PVDF composites were synthesized by the sol-gel method. By adjusting the mass ratio of BaFe12O19 and PVDF, the shell size of the BaFe12O19@PVDF composite material was controlled, and its electromagnetic absorption performance was enhanced. The shell thickness of BaFe12O19@PVDF is 19.64 nm when the BaFe12O19: PVDF mass ratio is 1:1.0, and the optimal impedance matching is obtained at 13.4 GHz. Meanwhile, at a thickness of 1.5 mm, the minimum reflection loss (RLmin) reached -58.04 dB, and an effective absorption bandwidth (EAB) (RL ≤ -10 dB) of 5.53 GHz was achieved within the frequency range of 11.65 to 15.63 GHz and from 16.36 to 17.91 GHz. Besides, the composites with a matching thickness of 3.5 mm show a maximum EAB of 15.90 GHz when the mass ratio of BaFe12O19 to PVDF is 1:1.2. Within the frequency range of 2-18 GHz, the coverage of reflection loss less than -10 dB is 99.38%, almost achieving full coverage. These results demonstrate that BaFe12O19@PVDF composites exhibit excellent electromagnetic-absorbing performances, making them an excellent candidate for electromagnetic wave absorption in 5G communications.

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.

Frequency tunable Ni–Ti‐substituted Ba–M hexaferrite for efficient electromagnetic wave absorption in 8.2–75 GHz range

The development of 5G telecommunication technology has seen a high demand for effective electromagnetic (EM) wave absorbers in the millimeter wave (mmWave) band. Because hexagonal M‐type ferrite is known to have high ferromagnetic resonance (FMR) in the 5G band frequency, it has attracted significant attention as a mmWave absorber. However, study of the relationship between magnetocrystalline anisotropy, FMR frequency, and EM wave absorption performance in the mmWave band remains insufficient. In this study, Ni–Ti‐substituted M‐type barium ferrite (Ba–M ferrite) was synthesized using the citrate sol–gel method, and the change in the magnetic properties caused by Ni–Ti substitution was analyzed. The complex permittivity, permeability, and reflection loss (RL) of the Ni–Ti‐substituted Ba–M ferrite composites in the 8.2–75 GHz broadband frequency range were also studied. The EM wave absorption frequency, which is governed by the FMR frequency, could be tuned by controlling the amount of substituted Ni–Ti ions in the Ba–M ferrite. The prepared EM wave absorber exhibited excellent EM wave absorption properties with an RL of −52 dB at 29.5 GHz and a matching thickness of 0.95 mm. This study provides insights into a frequency‐tunable EM wave absorber with enhanced absorption properties, attained by changing the magnetic properties of Ni–Ti‐substituted M‐type hexaferrites in the mmWave frequency band.

Rare earth Nd3+ ions-doped W-type barium ferrite for efficient microwave absorption and its optimization mechanism

Rare earth Nd3+ ions-doped W-type barium ferrite for efficient microwave absorption and its optimization mechanism

Magnetic properties of Sm-doped M-type barium ferrite by high-energy ball mill-assisted solid-phase reaction method

The primary objective of this study is to enhance the overall magnetic properties of pure barium ferrite through the addition of trace amounts of the light rare earth element Sm. This approach is more cost-effective compared to using heavy rare earth elements. The M-shaped barium ferrite, denoted as Ba1−xSmxFe12O19, was synthesized using a combination of solid-phase sintering method and high-energy ball milling. The high purity of samples was confirmed by determining their crystal structure using XRD. The internal structure of samples was examined using FTIR, and it was observed that the samples contained tetrahedral and octahedral clusters with corresponding bands at 599 cm−1 and 445 cm−1, respectively. The appearance of samples was examined using FESEM, and it was found that grains had hexagonal structures. EDS was used to characterize the elemental content of samples, and it was found that the content of Ba decreased with an increase in the content of Sm. The magnetic properties of samples were examined using VSM, and the coercivity reached a maximum value of 3096.22 Oe at a dopant fraction of 0.06, and the saturation magnetization reached a maximum value of 73.115 emu/g. The synthesized material has the potential for utilization in magnetic recording applications.

BaFe12O19/graphene/polyaniline coatings for flexible fabrics with enhanced microwave absorption

In this study, barium ferrite (BaFe12O19) was used as the basic microwave-absorbing material and compounded with graphene and PANI. Then, BaFe12O19, BaFe12O19/graphene, and BaFe12O19/graphene/PANI were mixed with waterborne polyurethane and coated on nylon fabrics by the cast coating method to prepare flexible microwave absorbing materials. The microwave absorbing performance of BaFe12O19/graphene/PANI coated fabric is significantly improved in comparison with BaFe12O19 and BaFe12O19/graphene coated fabric, which mainly comes from the synergistic effects of magnetic loss, dielectric loss, and conductivity loss. The BaFe12O19/graphene/PANI coated fabric has a minimum reflection loss value of –37.36 dB (at 13.76 GHz) and an effective absorption bandwidth of 5.40 GHz (12.44–17.84 GHz) when the thickness is 1.2 mm. Consequently, the facile preparation route and excellent performance make the BaFe12O19/graphene/PANI composite a promising candidate for efficient microwave absorbence.

Application of Steinmetz Formula in M-Type Barium Ferrite

Application of Steinmetz Formula in M-Type Barium Ferrite

Modifying the Local Structure and Properties of Zinc-Substituted Hexagonal Barium Ferrites for Microwave Devices via Magnetic Pulse Processing

Modifying the Local Structure and Properties of Zinc-Substituted Hexagonal Barium Ferrites for Microwave Devices via Magnetic Pulse Processing