BaM Ferrite Research Articles

Experimental Determination of Anisotropy Fields, First and Second Anisotropy Constants, and Remanent Magnetizations in Self-Polarized Zn–Ti and Co–Ti Equally Co-Substituted BaM Ferrites

M-type hexagonal barium ferrites Ba(M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> )Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12-2<i>x</i></sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> (M = Co or Zn, x = 0–0.5) were synthesized by chemical topotactical reaction. Both randomly oriented and self-polarized samples were prepared. Experimental values of the anisotropy fields, first and second anisotropy constants, and remanent magnetizations were extracted by combining hysteresis loops and microwave measurements. A salient result of this study is that, compared with K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cannot be disregarded for these co-doped BaM hexaferrites, even at low doping levels. Results show that the BaM ferrites of composition Ba(Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> )Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12-2<i>x</i></sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> are more suitable for microwave applications that operate at frequencies between 30 GHz and 40 GHz.

Microstructure and gyromagnetic properties of low-sintered M-type barium hexagonal ferrite with various Ga3+ ions substitutions

The adjustment of crystal structures and properties by ion substitution has received increasing interest in recent years to solve issues related to the preparation of LTCC microwave devices. In this work, Fe3+ ions were substituted in BaFe12O19 sintered at a low temperature (920 °C). The changes in microstructures, dielectric characteristics, and magnetic properties were all examined. The ferromagnetic resonance linewidth (ΔH) of BaM ferrite was measured at magnetic fields from 6000 to 24,000 Oe. The results revealed well-grown microstructures of BaM ferrite grains at 920 °C to form typical hexagonal structures. The increase in substitution of Ga3+ ions decreased the lattice constant and cell volume of the crystals. More interestingly, the dielectric and magnetic properties depicted significant changes in the original dielectric and magnetic parameters of BaM after the substitution of Ga3+ ions. The permittivity (ε′) rose to a maximum of 16.36 at x = 0.4, while the dielectric loss angle tangent (tan δε) declined to 1.2 × 10^−3. As Ga3+ ions rose, the saturation magnetization 4πMs decreased from 3168.58 Gauss to 2571.18 Gauss. The remanence (Mr) reached a maximum value of 31.07 emu/g at x = 0.4. The ferromagnetic resonance linewidth (ΔH) of BaM ferrite sample at 31 GHz attained a minimum value of 4216.336 Oe at x = 0.8. In sum, these findings look promising for future fabrication of LTCC microwave RF devices.

Adsorptive removal of methyl blue dye through magnetically retrievable BaFe12O19-activated charcoal-chitosan composite powder: kinetics, isotherms and thermodynamics studies

ABSTRACT BaFe12O19 (BaM) hexaferrite was synthesised through the coprecipitation method. BaFe12O19-activated charcoal-chitosan (BaM-AC-CS) composite was synthesised through ultra-sonication assisted water in the oil microemulsion method. Morphology of BaM hexaferrite, activated charcoal, and BaM-AC-CS composite powder was evaluated using FESEM. The average particle size of the composite powder was 60 µm. BaM-AC-CS composite powder exhibited a surface area of 41.5 m2 g −1 and pore volume of 0.041 cm3 g−1. The magnetic behaviour of BaM and BaM-AC-CS composite was analysed using a vibrating sample magnetometer. Pure BaM ferrite showed saturation magnetisation (Ms) of 69.3 emu g −1 and coercivity of 2670 Oe. BaM-AC-CS composite powder showed a Ms value of 26.8 emu g −1 which was sufficient for efficient magnetic separation of it in water suspension. The point of zero charge (pHpzc) of composite powder was 6.7. The composite powder was used for the adsorption of methyl blue (MB) dye solution of pH of 6 at 303, 313 and 323 K respectively. The dye removal capacity increased with increase in temperature. The adsorption process followed pseudo-second-order kinetic model and satisfied Redlich-Peterson as well as Sips adsorption isotherm. The composite powder showed a maximum Sips adsorption ability of 254.6 mg g −1 at 323 K temperature. The free energy and enthalpy changes confirmed the spontaneous and endothermic nature of the adsorption. The composite powder also showed good adsorption capacity in five consecutive regeneration cycles. All these results suggest that the BaM-AC-CS powder will be a viable material for MB dye adsorption in wastewater treatment.

Effect of sintering temperature on microstructure and magnetic and dielectric properties of M-type barium ferrites

In this study, the effect of sintering temperature on microstructure, magnetic properties and dielectric behavior of M-type barium ferrites (BaM) is systematically analyzed. BaBi0.45(CoTi)1.2Fe9.15O19 samples with a dense microstructure and typical hexagonal shape are obtained at the sintering temperature of 920 °C. Moreover, the permittivity (ε′) of BaM increases to 21.41 at 0.01 GHz and the permeability (μ′) increases to 10.82 at the optimized temperature of 920 °C. Based on mathematical fitting, the saturation magnetization (4πMs) of samples is calculated to be 3272.27 Gauss and the magnetocrystalline anisotropy constant K1 is found to be 4.18 × 106 erg cm−3. More interestingly, the magnetic loss angle tangent (tanδμ) is reduced to 2.7 × 10−1 and the dielectric loss angle tangent (tanδε) is reduced to 5.8 × 10−3. The optimized magnetic and dielectric properties, with low losses, enhance the suitability of BaM ferrites for miniaturized microstrip devices.

Adsorption and sunlight-induced photocatalytic degradation of methyl blue by BaFe12O19 ferrite particles synthesised through co-precipitation method

ABSTRACT BaFe12O19 (BaM) hexagonal ferrite was synthesised through the co-precipitation route. The thermal decomposition behaviour of co-precipitated powder was studied by DSC-TG. XRD and Raman analysis confirmed the formation of pure BaM phase at 900°C calcination temperature. Morphological analysis was done using FESEM. The magnetic behaviour of BaM was analysed using a vibrating sample magnetometer. The saturation magnetisation (Ms) of 67.7 emu g−1 and coercivity of 5106 Oe was observed in BaM. BaM ferrite with a surface area of 8.2 m2 g−1 was used for the adsorption of methyl blue (MB) and sunlight-induced photodegradation. The optical band gap of the ferrite was ~2.9 eV. The adsorption process followed the pseudo-second-order model and satisfied Langmuir adsorption isotherm. BaM particles showed the maximum Langmuir saturation adsorption ability of 223.86 mg g−1 at an initial MB solution pH of 5.7. The free energy and enthalpy changes of the adsorption confirmed the spontaneous and exothermic nature of the process. About 73% of degradation of MB was found within 3 h of sunlight-induced photocatalytic degradation. Reproduced BaM powder showed high adsorption and degradation efficiency even after five cycles. All these results suggest that BaM particles can be used as a promising material for the adsorption and degradation of MB in wastewater treatment.

A Study on Synthesis, Structural and Magnetic Properties of La2O3 Doped Isotropic Ba-M Ferrites

A Study on Synthesis, Structural and Magnetic Properties of La2O3 Doped Isotropic Ba-M Ferrites

Suppressed domain wall damping in planar BaM hexaferrites for miniaturization of microwave devices

CoRu-substituted BaM hexaferrites, with additives of Bi2O3, demonstrate low losses and high permeability above 1 GHz. The RuCo- and BiRuCo-doped BaM ferrites were prepared by conventional solid-state reaction methods. Magnetic spectra indicate that there were two peaks in the imaginary part of the permeability spectra which originate from domain wall motion and spin rotation. Compared to the RuCo-BaM sample, BiRuCo-doped BaM samples exhibit slight decreases in permeability (~2.9), but the magnetic loss tangents decrease markedly by 47% to ~0.05 at 1 GHz while retaining a low magnetic loss ~0.1 up to 1.5 GHz. From fitting to experimental data, it’s clear that the reduction of magnetic loss stems predominantly from a suppressed domain wall damping due to the introduction of Bi2O3. It is demonstrated that Bi2O3 can effectively control the microstructure of polycrystalline ferrites, and in turn tailor the contribution of domain wall resonance or spin rotation to permeability and magnetic loss. The results are valuable to the engineering of ferrite materials for use in the miniaturization of wide band microwave antenna at operating frequencies up to 1 GHz.

Synthesis and characterization of BaFe12O19-CoFe2O4 ferrite composite for high-frequency antenna application

Recently, ferrite composite ceramics have received much attention for high-frequency device applications as the composite has both dielectric and magnetic properties, good chemical stability, and high electrical resistivity. M-type hexagonal ferrite BaFe12O19 (BaM) and cubic spinel ferrite CoFe2O4 (CoF) composites; (BaM)1−x(CoF)x (x = 0.0, 0.25, 0.50, 0.75, and 1.0) were successfully synthesized by co-precipitation method. X-ray diffraction (XRD) analysis confirmed the formation of pure-phase BaM ferrite at 800 °C and CoF ferrite at 600 °C, respectively. The XRD analysis of composite ferrite showed the presence of both BaM and CoF ferrite phases in the composite. The composites were sintered at 1100 °C/4 h. The composite with x = 0.25 composition showed the most compact microstructure structure and higher bulk density compared to other composites. The composite (with x = 0.25) also showed the highest permittivity (~ 15), permeability (~ 13), and antenna miniaturization factor (~ 14) at 500 MHz due to mainly better densification. The permeability of composite was almost stable up to about 500 MHz. The coercivity was lowest in the composite with x = 0.25 composition indicating a change of hard magnetic behavior of BaM ferrite into a soft magnetic character after composite formation, which may be due to the formation of enlarged grain of BaM in the composite.

Molten salt synthesis, formation mechanism and greatly enhanced magnetic properties of randomly oriented BaM ferrite

Due to the influence of specific preparation process and product microstructure characteristics, it is a difficult task to prepare the randomly oriented BaFe12O19 (BaM) ferrite with large remanent magnetization (Mr) and high saturation magnetization (Ms), which hinder the practical application of the BaM ferrite. One of the means to solve this problem is to prepare well-developed hexagonal plate-like structure and single magnetic domain particles by lower synthesis temperature. In this study, the BaM ferrite were prepared using molten salt synthesis (MSS) method, and the preparation conditions of excellent magnetic properties and the formation mechanism of BaM ferrite synthesized by molten salt were discussed. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and magnetic properties analyses indicated that the BaM ferrite with greatly enhanced magnetic properties could be obtained by adjusting the calcination temperature, Fe3+/Ba2+ molar ratio and the salts to reactants mass ratio R. The Ms and Mr of the prepared BaM ferrite were 71.9 emu/g and 39.5 emu/g, respectively. The Ms of the prepared BaM ferrite was significantly enhanced, and the Mr was much higher than that of BaM ferrite prepared by other methods. Using hydrothermal method synthesized spindle-like α-Fe2O3 as a raw material confirmed that the formation mechanism of molten salt synthesis of BaM ferrite was dissolution and precipitation mechanism. The formation of BaM ferrite underwent a series of processes including BaFe2O4 and BaFe4O7 formation, iron oxide dissolution, BaFe2O4 and BaFe4O7 desolvation of Ba2+, ion diffusion, nucleation growth and precipitation.

Influence of Sc3+ substitution on magnetic properties of c-axis textured M-type barium ferrite

In this paper, C-axis textured M-type barium ferrite BaScxFe12−xO19 (x = 0.2, 0.5, 0.7, 0.9, 1.1) have been synthesized via the solid-state method. Results of the SEM reveal that the Sc3+ has no obvious effect on the crystal morphology. However, Sc3+ ion have remarkable effect on tailor the magnetic properties of BaM ferrite. The measured results for the vibrating sample magnetometer indicate that increasing x of the induced Sc3+ yields decreasing the magneto-crystalline anisotropy field, saturation magnetization, coercivity, and reduces the squareness ratio. The site preference mechanism of Sc3+ on Fe3+ site in BaM hexaferrite crystal structure is also discussed.

Microwave absorption properties of hexagonal barium doped @cip composite in wide band

M-type (BaM) hexagonal ferrite with chemical composition Ba1.0Mn0.5Co0.5Ti1.0Fe10O19 synthesized by solid state reaction. The XRD Pattern of BaM confirms the formation of hexagonal ferrite without any other impurity phases. The particle size and surface morphology has been analyzed by SEM characterization, which reveals the hexagonal morphology of Ba1.0Mn0.5Co0.5Ti1.0Fe10O19, with average size of 10 micron. The XRD pattern and SEM images of purchased Carbonyl Iron Powder (CIP) shows single phase of CIP with average size of 5 micron with spherical morphology.The XRD Pattern of BaM@CIP reveals the formation of composite, in which both phases are coexistant with CIP particles are connected with hexagonal particles of BaM to enhance the interfacial polarization due to accumulation of charges at the interfaces and improve the absorption of EM waves. The magnetic properties of pristine BaM, CIP and their composites has been studied at room temperature by Vibrating Sample Magnetometer (VSM), the M-H loop of composite sample shows increase in coercivity due to exchange spring effect produce in hard and soft magnetic composite materials. For RCS measurement, the pristine BaM ferrite and its composite with 50% (CIP) mixed with a suitable ratio of epoxy and harden, applying on a metallic surface. The Reflection loss results of composite BaM@CIP shows enhancement in widening the band width (7.75–12.5 G Hz) at a minimum thickness of 1.2 mm.

A Current Review on the Synthesis and Magnetic Properties of M-Type Hexaferrites Material

After the discovery of hexagonal ferrites or hexaferrites, it has been become important materials commercially and technically to study which is still growing on. In this article, we have reviewed about the M-type hexaferrites including their structural, synthesis techniques and important magnetic properties. The role of experimental synthesizing techniques adopted for preparation of M-type hexaferrites on the various parameters studied in this review paper. The substitution of holonium in BaM ferrite reduces the value of coercivity but not saturation magnetization and ramanence and the cobalt-titanium substituted ferrites were the most important M-type ferrites in the field of application in microwave properties and magnetic field industry.

Enhanced and broadband microwave absorption of flake-shaped Fe and FeNi composite with Ba ferrites

In order to achieve a broad bandwidth absorber at high frequency, the composites of M-type ferrite BaCo1.0Ti1.0Fe10O19 (BaM) with flaked carbonyl iron powders (CIP) and flaked Fe50Ni50 were prepared to optimize the surface impedance in broadband frequency, respectively. The diameter of the flaked carbonyl iron powders (CIP) and Fe50Ni50 is in the range of 5–10µm and 10–20µm and the thickness of the CIP and Fe50Ni50 is close to 200nm and 400nm, respectively. The complex permeability and permittivity show that the addition of BaM obviously reduces the values of real part of permittivity and imaginary part of the permeability which can enhance the matched-wave-impedance. The absorption bands less than −10dB of CIP-BaM and FeNi-BaM absorber approach to 5.5GHz (5.7–11.2GHz) and 7GHz (11–18GHz) at 1.5mm. However, the bands of CIP and FeNi are only 1.9GHz (4.7–6.6GHz) and 2.1GHz (4.0–6.1GHz). Hence, the electromagnetic match property is greatly improved by BaM ferrites, and this composite shows a broaden absorption band.

Enhanced saturation magnetization and microwave absorption magnetic properties of Mn-Co-Zr substituted BaM ferrite

Mn-Co-Zr substituted BaM ferrite with enhanced saturation magnetization (Ms) was prepared by so-gel method for high-frequency applications. The substituted single-phase BaM ferrite is prepared by heat treating at 1100 °C for 4 h. We used SEM, XRD and VSM (vibrating sample magnetometer) to study the sample's morphology, phase and magnetic properties. SEM result shows the ferrite particle size is reduced from 250 nm to 35 nm as substitution x = 1.2. Though BaM ferrite is traditionally a permanent magnetic material, VSM measurements indicate it becomes soft magnetic material after substituting the Mn-Co-Zr ions. The coercivity (Hc) and Ms are 3658 Oe and 58.8 emu/g for x = 0.2, and it becomes 317 Oe and 48.7 emu/g for x = 1.2. Vector network analyzer (VNA) was employed to investigate the high-frequency electromagnetic properties of the ferrite. It was found that the resonance peak decreases as x increases. The reflection loss (RL) is smaller than 10 dB for frequency ranges of 7.2–12.2 GHz and smaller than 20 dB for 9.1–10.6 GHz. The maximum RL is 23 dB at frequency of 9.7 GHz for x = 1.2. Mn-Co-Zr substituted BaM ferrite might be a good candidate for electromagnetic compatibility and for other applications at high frequencies.

Magnetic Properties and Microstructures of Cobalt Substituted Barium Hexaferrites Derived from Steel Waste Product via Mechanical Alloying Technique

The mechanical alloying technique was used to prepare barium hexaferrite (BaM) with 3, 5, 10 and 20 wt% cobalt oxide (Co3O4). In this work, steel waste flakes were cold-rolling steel mill for several hours to form a fine powder. The steel waste powder was purified by using magnetic separation to isolate the magnetic and non magnetic particles. The method was continued for Curie temperature separation technique to separate the magnetic ions by varied Curie temperature of the magnetic powder. The purified powder was then oxidize at 500 °C at 6 °C/mins to form hematite, Fe2O3. The steel waste-derived hematite was used as the raw material in preparing BaM ferrites. The BaCO3, Fe2O3 and different percentages of Co3O4 (Co) were mixed and milled for several hours by using mechanical alloying. The powder were pelletised in 11 × 1 mm (diameter × height) and the sintered at 1200 °C for 10 hours. The addition of Co2+/3+ ions to the BaM shows a varying in the magnetic properties of BaM. By increasing the Co doping, the remanence Mr was reduced from 17.6 emu/g to 6.2 emu/g. The coercivity Hc results varying magnitude from 102 Oe to 1079 Oe. The Mr and Hc of undoped BaM is obtain at 14.6 emu/g and 860 Oe, respectively. The grain size of BaM also increases with Co doping. The densities of the compounds are decreasing with increasing Co doping with a maximum value of 4.2 g/cm3.

Magnetic and microwave properties of U-type hexaferrite films with high remanence and low ferromagnetic resonance linewidth

U-type barium hexaferrite films (Ba4Ni1.4Co0.6Fe36O60) were deposited on (0001) sapphire substrates by pulsed laser deposition. Microstructure and magnetic properties of the films were characterized by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. Ferromagnetic resonance (FMR) measurements were performed at X-band. The results indicate an anisotropy field of ∼8 kOe, and the saturation magnetization (4πMs) of ∼3.6 kG. An optimal post-deposition annealing of films results in a strong (0 0 n) crystallographic texture and a high hysteresis loop squareness (Mr/Ms = 92%) leading to self biased properties. Furthermore, the highly self-biased ferrite films exhibited an FMR linewidth of ∼200 Oe. The U-type hexaferrite films having low microwave loss, low magnetic anisotropy field, and high squareness are a suitable alternative to Sc or In doped BaM ferrites that have been the choice material for self-biased microwave devices at X-band frequencies.

ChemInform Abstract: Hexagonal Ferrites: A Review of the Synthesis, Properties and Applications of Hexaferrite Ceramics

AbstractReview: 560 refs.

Synthesis, characterization and magnetic properties on nanocrystalline BaFe 12O 19 ferrite

Single phase BaM (BaFe 12O 19) ferrites are prepared by using sol–gel method. The preparing conditions of samples are investigated in detail, such as acid/nitrate ratio, the value of pH and annealing temperature. The best conditions on preparing BaFe 12O 19, which can be obtained on a Fe/Ba ratio of 12, the citric acid contents R = 3, the starting pH of solution is 9, and annealing temperature 950 °C. The thermal decomposition behavior of the dried gel was examined by TG–DSC, the structure and properties of powders were measured respectively by XRD techniques. The magnetic properties of barium ferrites are emphatically researched about the changing crystallite size and annealing temperature by the vibrating sample magnetometer (VSM). Magnetic measurement shows that the barium ferrite samples annealed at 1000 °C has the maximal coercive field of 5691.91 Oe corresponding to the maximal remnant magnetization of 35.60 emu/g and the sample synthesized at 1000 °C has the maximal saturation magnetization of 60.75 emu/g.

Perpendicularly Oriented Polycrystalline BaFe11.1Sc0.9O19 Hexaferrite with Narrow FMR Linewidths

We demonstrate low ferromagnetic resonance (FMR) linewidths and high remanence magnetization in polycrystalline M‐type Sc‐doped Ba ferrites having anisotropy fields of ∼8 kOe and perpendicular orientation of the spontaneous magnetization vector. This is a result of applying a unique processing technique that makes use of a polymer network‐assisted alignment of hexaferrite particles in high magnetic fields. The resulting compacts exhibit high squareness (Mr/Ms∼92%) and low FMR linewidths (∼530 Oe) at X‐band and Ka‐band. This represents an ∼74% decrease in linewidth compared with previous reports for polycrystalline BaM ferrites using conventional processes. We also have detailed origins of the FMR linewidth broadenings in terms of some important theoretical models. These materials have potential for use in low frequency self‐biased microwave/millimeter devices such as circulators and isolators.

Efeito da variação estequiométrica na formação de ferritas BaM produzidas pelo método SHS e pelo método cerâmico tradicional

As ferritas do tipo BaM são cerâmicas ferrimagnéticas, usualmente aplicadas em sistemas de gravação magnética e como magnetos duros. Possuem alta estabilidade química, resistência a corrosão e baixo custo de produção. Diante da sua crescente importância, foi estudado o efeito da contribuição do excesso de bário no processamento e formação da fase ferrita BaM por duas distintas rotas: processamento por mistura de óxidos e a síntese por reação de combustão (método SHS) com o uso de carbonato e nitrato de bário. Duas relações de concentração entre bário e ferro foram utilizadas, uma estequiométrica (n = Fe2O3/BaO = 6) e uma outra não estequiométrica (n = Fe2O3/BaO = 5,45). Os pós processados com excesso de bário resultaram na presença da fase intermediária de formação BaFe2O4, a qual permanece após altas temperaturas de calcinação e mesmo após a sinterização de compactos obtidos a partir dos pós calcinados. As conclusões foram baseadas em difratogramas de raios X das ferritas BaM em pó após calcinação e nas amostras conformadas e sinterizadas, além de imagens obtidas por microscopia eletrônica de varredura. Os resultados de medidas magnéticas indicam a diminuição da coercividade, da indução magnética remanente e dos valores de BH Máx dos pós obtidos com a contribuição do excesso de bário, provavelmente devido à presença da fase intermediária não magnética. Este efeito negativo foi mais efetivo nos pós processados pelo método SHS, chegando a uma redução de 28,8% no valor de coercividade e 35,1% no valor de BH Máx. Os pós de ferritas BaM obtidos pelo método cerâmico tradicional apresentaram maiores valores de coercividade (4,28 kOe) e BH Máx (0,87 MOe*emu/g) e a influência do excesso de bário na formulação foi menos prejudicial sobre suas propriedades magnéticas.