Soft Ferrites Research Articles

Structural and magnetic properties of gadolinium substituted Mn0.6Zn0.4GdxFe2−xO4 (x = 0–0.1) spinel ferrite

Soft magnetic ferrites Mn0.6Zn0.4GdxFe2-xO4 (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) have been synthesized using a solvothermal method. X-ray diffraction analysis revealed the structure of Gd3+ doped Mn-Zn ferrite was spinel structure. In response to an increase in Gd3+ content, the lattice constant of the sample increased and then decreased, and the largest lattice constant was 8.452 Å with x = 0.04. The crystallite size varied between 14.7 and 18 nm. M−H data revealed that all samples are soft magnetic and characterized by the larger saturation magnetization, low remnant magnetization and coercively. We found that the Gd3+ ions substituted into Fe3+ ion sites and resulted an increase in Gd3+ content from x = 0 to x = 0.1, which lead to the saturation magnetization first increased then decreased. The maximum saturation magnetization value of Mn0.6Zn0.4GdxFe2-xO4 was 90.1 emu/g with x = 0.04, which suggested the Mn0.6Zn0.4Gd0.04Fe1.96O4 was magnetically responsive, and could be used in hyperthermia tumor applications.

Hysteresis loss free soft magnetic ferrites based on Larmor precession

Abstract A big enough transverse magnetic field applied in soft magnetic ferrite toroid can magnetize the ferrite to saturation in transverse direction and almost completely suppresses magnetic domain structures in the ferrite, the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field and the hysteresis loss disappears in the ferrites. Both theoretical and experimental results indicate that the permeability and magnetic losses in the ferrite can be tuned by adjusting the transverse magnetic field. A higher Q value with relatively lower permeability can be achieved by increasing the transverse field, which ensures the ferrite can be operated at high frequencies with very low magnetic losses.

Core/shell \(\textbf{CoFe}_{2}\textbf{O}_{4}/\textbf{Fe}_{3}\textbf{O}_{4}\) Nanoparticles: Effects of Hard/soft Magnetic Weight Fraction on Structure, Particle Size and Magnetic Properties

CoFe\(_{2}\)O\(_{4}\)/Fe\(_{3}\)O\(_{4}\) nanocomposite particles were synthesized by using co-precipitation combined with hydrothermal methods. The phase composition, surface morphology and magnetic properties of the nanocomposites were investigated using X- ray diffraction, scanning electron microscopy and vibrating sample magnetometer. Findings show that the samples comprise two phases, and Fe\(_{3}\)O\(_{4}\) particles are coated on the surface of CoFe\(_{2}\)O\(_{4}\) particles. The average particle size of CoFe\(_{2}\)O\(_{4}\) was ditrisbuted in the range of 50 -- 100 nm. While the particle of Fe\(_{3}\)O\(_{4}\) displayed a spherical shape and particle size distributed from 10 -- 20 nm. The MS of CoFe\(_{2}\)O\(_{4}\)@Fe\(_{3}\)O\(_{4}\) core–shell particles increase with the decrease in the mass ratio of hard to soft ferrites. The structure, magnetic properties and the degree of exchange coupling between the magnetic phases were investigated.

Curing, Properties and EMI Absorption Shielding of Rubber Composites Based on Ferrites and Carbon Fibres.

In this work, magnetic soft ferrites, namely manganese-zinc ferrite, nickel-zinc ferrite and combinations of both fillers, were incorporated into acrylonitrile-butadiene rubber to fabricate composite materials. The total content of ferrites was kept constant-300 phr. The second series of composites was fabricated with a similar composition. Moreover, carbon fibres were incorporated into rubber compounds in constant amount-25 phr. The work was focused on investigation of the fillers on absorption shieling performance of the composites, which was investigated within the frequency range 1-6 GHz. Then, the physical-mechanical properties of the composites were evaluated. The achieved results demonstrated that the absorption shielding efficiency of both composite types increased with increasing proportion of nickel-zinc ferrite, which suggests that nickel-zinc ferrite demonstrated better absorption shielding potential. Higher electrical conductivity and higher permittivity of composites filled with carbon fibres and ferrites resulted in their lower absorption shielding performance. Simultaneously, they absorbed electromagnetic radiation at lower frequencies. On the other hand, carbon fibres reinforced the rubber matrix, and subsequent improvement in physical-mechanical properties was recorded.

Tuning structural, electrical, dielectric and magnetic properties of Mg–Cu–Co ferrites via dysprosium (Dy3+) doping

In current research work, Dy3+ substituted Mg0.5Cu0.25Co0.25Fe2‒xDyxO4 (0.0 ≤ x ≤ 0.04 with the step interval of 0.01) soft ferrites were synthesized by the sol–gel auto combustion method. The prepared samples were characterized by the techniques using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, current–voltage (I–V) measurement, LCR meter, vibrating sample magnetometer (VSM) and Raman. XRD data reveal that the average crystallite size is 49.71 nm and the lattice constant is 0.83703 nm for sample x = 0.03. The non-uniform grain growth was demonstrated by micrographs and impurity-free elemental composition was observed from EDX analysis. The DC resistivity has an increasing and decreasing trend in ferromagnetic and paramagnetic regions with an increase in temperature. Moreover, the high resistivity is observed with the order of 1010 Ω·cm, and the activation energy is 0.944 eV for samples x = 0.03. The dielectric parameters including dielectric constant, dielectric losses, and impedance gradually decrease with the increase in frequency from 8 Hz to 8 MHz. The minimum dielectric loss at high frequency is found for sample x = 0.03. The coercivity (Hc) and saturation magnetization (Ms) are found in the ranges of 520.82–544.02 Oe and 20.5841–21.1473 emu/g, respectively. These observations confirm that dysprosium (x = 0.03) doped MCC-soft ferrites may be applicable in transformer cores, microwave absorbance, and telecommunication devices.

Producing Soft Magnetic Composites by Spark Plasma Sintering of Pseudo Core-Shell Ni-Fe Alloy@Mn0.5Zn0.5Fe2O4 Powders.

Soft magnetic composite (SMC) cores have been obtained by Spark Plasma Sintering (SPS) using pseudo core-shell powders. Pseudo core-shell powders are formed by a core of soft magnetic particle (nanocrystalline permalloy or supermalloy) surrounded by a thin layer (shell) of nanosized soft ferrite (Mn0.5Zn0.5Fe2O4). Three compositions of pseudo core-shell powders were prepared, with 1, 2 and 3 wt.% of manganese-zinc mixt ferrite. The pseudo core-shell powders were compacted by SPS at temperatures between 500 and 700 °C, with a holding time ranging from 0 to 10 min. Several techniques have been used for characterization of the samples, both, powders and compacts X-ray diffraction (XRD, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), magnetic hysteresis measurements (DC and AC) and electrical resistivity. The electrical resistivity is in the order of 1 × 10-2 Ωm, 3-4 orders of magnitude higher than supermalloy electrical resistivity. The SPS at lower temperatures (500 °C) conserves the initial phases of the composite, but increasing the sintering temperature and/or sintering time produces a solid-state reaction between the alloy and ferrite phases, with negative consequence on the magnetic properties of the compacts. The initial relative permeability is around 40 and remains constant until to 2000 Hz. The power losses are lower than 2 W/kg until to 2000 Hz.

Evaluation of molecular transport mechanism and interfacial interactions in doped ferrite rubber composites

Nickel ferrites (NIFs) come under the class of soft ferrites or transformer ferrites, which are highly demanding in the electronics industry and possess usual low conductivity and ferromagnetic properties, which results in decreased eddy current losses, good electrochemical stability, catalytic action, and abundance in nature. We discuss the synthesis, characterization, and impact of synthesized NIF fillers on the mechanical and solvent transport characteristics of rubber composites. Doped ferrite composites made of natural rubber and nitrile rubber were cured at various temperatures, and the solvent swelling properties of composites containing differently doped NIFs were examined in aromatic solvents like toluene. Properties of both rubber composites were examined, including their morphology, solvent uptake, diffusion coefficient, transport mechanism, and thermal stability. Natural rubber composites found to have better swelling properties than that of nitrile rubber composites. The solvent uptake was reduced with increase in filler loading also, the increase in sorption temperature increases the swelling rate in both systems. Theoretical calculations and modelling clearly state that the diffusion mechanism is due to the polymer swelling as well as polymer relaxation.

Structural, optical and electrical impacts of Ni2+ on Mg1-xFe1.9Sm0.1O4 (x = 0.0, 0.2, 0.4 and 0.6) spinel ferrites

Sol-gel auto combustion was used to create a sequence of soft ferrites, NixMg1- xFe1.9Sm0.1O4(x = 0.0, 0.2, 0.4 & 0.6). The XRD, FTIR, UV-vis, & four probe I-V techniques, respectively, were used to evaluate the structural, optical, and electrical properties. The cubic crystal structure was confirmed by the XRD pattern. The range of 25.71 - 33.67 nm was found to be the average crystallite size. FTIR spectra provided evidence of the tetrahedral band's existence. With the enhancement of Ni2+ concentration, Eg was determined from 2.28-3.21 eV. It was confirmed by the ranges of DC electrical resistivity that materials might be used in transformers to lessen eddy current losses.

Microstructure and Properties of Press-Bonded Dissimilar Stainless Steel and Mild Carbon Steel Ingots

Dissimilar steel welds between stainless and mild steels are necessary for the efficient utilization of stainless steels in construction. In the present work, a dissimilar large-sized steel ingot was fabricated by press bonding a Q235 steel to a SUS 304 steel at 1100–500 °C. The microstructure of bonded interfaces has been characterized by scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy, together with tensile tests to evaluate the bonding strength. It has been demonstrated that a strong-bonded, high-quality, dissimilar steel ingot could be fabricated by press bonding. The (Fe, Cr)3C carbide is present in the narrow zone of diffusion-bonded stainless steel and mild steel. Interestingly, the maximum hardness is not too high to make the transition zone brittle but enough to constrain the narrow soft ferrite during tensile and fatigue tests, causing the final fracture to occur in the mild steel region rather than the bonding interface.

Study of morphology and magnetism of MnFe2O4–SiO2 composites

Mixed magnetic composites of manganese ferrite and cristobalite (MnFe2O4–SiO2) were produced by the solid-state reaction method, using as starting materials in natura ores found in the state of Rio Grande do Norte – Brazil. Based on the stoichiometric proportions of the precursor ores, various composites in the form of powders and pellets were synthesized at a temperature of 1200 °C/12h under ambient atmosphere. Samples in the form of pellets were made at compression pressures of 370 and 740 MPa to investigate the effect of pressure on the physicochemical, and dielectric properties of the material. Structural, morphological and magnetic analyses were studied for the series of samples. X-ray diffractogram (XRD) results confirmed the formation of the mixed spinel phase MnFe2O4 with cubic symmetry and space group Fd-3m:1, together with peaks corresponding to SiO2–cristobalite. The Rietveld refinements identified a predominance of about 90% of the MnFe2O4 phase with crystallite variations of 130–190 nm due to the effect of compaction pressure. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electronic microscopy (TEM) mappings show clusters of triangular crystals in the pellets series. Magnetic hysteresis cycles at room temperature show a fast magnetization saturation (MS) response in a field of ∼4 kOe, with parameters dependent on the size and shape of the crystallites. The magnetically soft ferrites exhibited very low coercive field values. The hysteretic curves measured at 5 K showed a significant gain in the MS of ∼30 emu/g. Analyzes of magnetization as a function of temperature identified a blocked regime with a maximum ∼97 K (powder) and ∼170 K (pellets), and an irreversibility of the ZFC–FC curves up to room temperature. An indication of a spin-glass (SG) like state close to 20 K can also be seen in these results. Dielectric characterization of the pellets was performed from 1.0 to 8.5 GHz, and presented well-defined behavior, where real permittivity can be highly related to Rietveld refinement of XRD, and SEM/EDS results. This research suggests the feasibility of producing manganese ferrite composites directly from minerals, without the use of high-purity chemical reagents, allowing their obtainment on a large scale for commercial use.

Exploring the structural, magnetic and magnetothermal properties of (CoFe2O4)x/(Ni0.8Zn0.2Fe2O4)1-x nanocomposite ferrites

The hard ferrite (CoFe2O4), soft ferrite (Ni0.8Zn0.2Fe2O4) and composite ferrite (CoFe2O4)x/(Ni0.8Zn0.2Fe2O4)1-x (hard/soft ferrite) with x = 0.2,0.4,0.6,0.8 were synthesized by sol-gel auto combustion method. X- Ray Diffraction analysis revealed the formation of the phases. The cubic structures of the samples were confirmed. The thermal analysis done using TGA/DSC confirmed the temperature of phase formation. The FTIR spectroscopy data for the samples were used to confirm the formation of functional groups and successful synthesis of the ferrites. The as-synthesized samples were characterized by SEM confirmed the overlapping spherical particles and elemental mapping was done with EDS. The FESEM and TEM analysis were done for the sample showing enhanced property of magnetic hyperthermia. The saturation magnetization (Ms), Coercivity (Hc) and the remanent magnetization (Mr) of the samples were studied using Vibrating Sample Magnetometry. The surface charge of the particles when dispersed in DI water was examined using Zeta potential measurement. Finally, we analysed the heating characteristics of the samples in an alternating magnetic field of frequency 350 kHz and field amplitude of 50 Oe. It has been concluded that the magnetic properties depend on the concentration of soft and hard ferrite in the samples and magnetic heating efficiency depends on the composition of the samples.

Study of structural, optical, photocatalytic, electromagnetic, and biological properties Co0.75Mg0.25CexFe2−xO4 of Mg-Co nano ferrites

Nano spinel ferrites with formula Co0.75Mg0.25CexFe2−xO4 (0 ≤ x ≤ 0.25 by step 0.05) were synthesized by using citrate gel auto combustion method and studied their structural characterization, optical studies, photocatalytic, biological and electromagnetic properties. Structural properties carried out by XRD, SEM, EDS, FTIR spectroscopy. The XRD studies confirm the crystalline size & lattice constant of Ce co-doped Co-Mg mixed nano ferrites. Morphology of the samples were examined by SEM and EDS analysis confirmed the proposed sample composition. FTIR spectral analysis help to confirm the formation of spinel structure in ferrite samples. Further optical studies confirm the band gap energy and cut off wavelength. Photocatalytic degradation of MB and AR dyes were carried out and good results were observed the degradation activity due to the catalyst heat treatment. Antibacterial studies confirmed that the nanoparticles are toxic to Bacillus subtilis, staphylococcus aureus (gram-positive strains) and Escherichia coli, Klebsiella pneumonia (gram-negative strains) Bacillus subtilis showed highest zone of inhibition of 13.3 mm. Saturation magnetization, coercivity, and remanence magnetization were calculated by VSM and Co0.75Mg0.25Ce0.25Fe1.75O4 was found to have high saturation magnetization that indicates that the sample behaves like a super para magnet. The Squareness of Co-Mg-Ce mixed nano ferrites initially decreases than increases hence the system changes from soft ferrites to hard ferrites. The electromagnetic properties such as AC conductivity (σAC), Dielectric constant (ε/), and impedance analysis are reported. The cole–cole plots shows the single semicircle behaviour.

Magnetic and Structural Properties of Manganese Zinc Soft Ferrite for High-Frequency Applications

Current work elaborates magnetic, microstructural, and thermal properties of Mn0.45Zn0.55Fe2O4 ferrite synthesized by the powder metallurgy method. Process parameters have been established to obtain ideal microstructure and magnetic properties at a frequency ranging from 1 kHz to 1000 MHz. Microscopic examinations revealed a uniform spinel structure containing grains size of 12 ± <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \,\mu \text{m}$ </tex-math></inline-formula> and free of nonmagnetic phases. X-ray diffraction studies evidenced cubic crystal structure for pure spinel MnZn ferrite. The Mn0.45Zn0.55Fe2O4 ferrite exhibits inductance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$A_{L}$ </tex-math></inline-formula> ) as 5425 nH, initial relative permeability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{i}$ </tex-math></inline-formula> ) as 5877, core loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{c}$ </tex-math></inline-formula> ) as 60.422 W/kg, and saturation magnetic polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{s}$ </tex-math></inline-formula> ) as 3.680 kG at a 1000-MHz applied frequency state. Surface coating was applied on toroid shape samples, which revealed a uniform coating thickness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$450 \,\mu \text{m}$ </tex-math></inline-formula> ) and tenacious appearance of coating layer. Thermal stability of coating was found to be stable up to 150 °C for 6 h. Coating exhibits 35±2 HV hardness and coefficent of friction (CoF) as 0.27, which indicates excellent adherence and high wear resistance of coating.

Effect of ferrite grain shape in friction element welds on cross tension strength

High-strength steels (HSSs) have been increasingly used in car bodies in order to simultaneously achieve the weight reduction and high collision safety of vehicles. In resistance spot welding, which is widely used for joining car bodies, low cross tension strength (CTS) of joints using HSSs is a problem. In our previous study, we focused on friction element welding (FEW) of HSSs to improve CTS and reported that the poor local ductility of the area quenched from two-phase temperature region (inter-critically annealed and quenched area) due to the presence of soft ferrite (α) and hard martensite (M) causes a decrease in CTS of FEW. The local ductility of steels with dual phase structure is known to be affected by the microstructural morphology. Therefore, in this study, we prepared joints of FEW with both the equiaxial α (C30) and the acicular α (C30L) in dual phase structure by controlling parent structures prior to the inter-critical annealing and quenching during FEW. C30L exhibited the higher CTS than C30. C30L fractured along the thickness direction of the lower sheet from the inter-critically annealed and quenched area near the edge of the joint to the softened area of heat affected zone, while C30 fractured along the inter-critically annealed and quenched area; however, the dimples were observed on the fracture surfaces irrespective of materials. Taking into account the fact that C30 and C30L showed no difference in the hardness distribution of the joints and the hardness difference between α and M hardness, it was suggested that morphology of α plays an important role in determining CTS. It is inferred that the local strain concentration in the inter-critically annealed and quenched area is relaxed by the presence of fine acicular α, which leads to the improvement of the local ductility, i.e. CTS.

Effect of Nd3+ ions on structural, spectral, magnetic, and dielectric properties of Co–Zn soft ferrites synthesized via sol-gel technique

The substitution of Neodymium (Nd) in the cobalt - zinc (Co–Zn) ferrite was analyzed. The sol-gel technique was used to synthesize these ceramic samples. The crystalline structural, molecular characterizations, and magnetic properties were analyzed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) experiments, and vibrating sample magnetometer (VSM) respectively. XRD patterns revealed the single-phase cubic spinel structure of the samples. Lattice parameter varied from 8.41 to 8.38 Å with the inclusion of Nd concentration. The existence of two characteristic frequency bands in the range of 400–1400 cm−1 was confirmed by FTIR spectra. VSM measurements showed the magnetic behaviour at room temperature. The saturation magnetization was noted to decrease from 81 to 66 emu/g with increasing the Nd concentration. The sample having step size x = 0.025 revealed the highest coercivity and retentivity. Dielectric properties were studied and showed variation in dielectric constant, dielectric loss, ac conductivity, and energy dissipation (tangent loss) in the prepared materials.

Concentration dependent exchange coupling in BaFe12O19/NiFe2O4 nanocomposites

Hard Barium ferrite (BaFe12O19) and soft Nickel ferrite (NiFe2O4) nanoparticles and their nanocomposites with different concentrations, i.e. (BaFe12O19)1−x/(NiFe2O4)x where x = 0, 0.3, 0.5, 0.7 and 1 were successfully synthesized. X-ray diffraction was used to obtain the phase formation and purity of these samples and the average crystallite size was found to be in a narrow range of 27–34 nm. The merging of zero field cooled and field cooled magnetization curves for x = 0.7 was evidence of strong magnetic interactions in these nanocomposites which is due to strong exchange coupling of hard/soft magnetic phase at this particular concentration. The value of coercivity and saturation magnetization of soft ferrite (NiFe2O4) should be linearly increased by the addition of hard ferrite (BaFe12O19), however a sharp increase was found for x = 0.7 and x = 0.5 samples, which is indication for the presence of spring exchange coupling in these nanocomposites. The single peak in dM/dH vs H plot indicate the presence of strong exchange coupling for x = 0.5. Bloch’s law fit revealed the smallest value of Bloch’s constant B for x = 0.7, which is also an evidence for the presence of strong magnetic interactions in these nanocomposites. The Kneller’s law fit to the HC versus temperature data revealed the higher value of Kneller’s constant α for x = 0.7, which may be due to presence of strong magnetic interactions in these nanocomposites. In summary, hard/soft ferrites nanocomposites with spring exchange mechanism strongly depends on the concentration of hard and soft ferrite phases and may be beneficial for different technological applications.

Magnetic Losses in Soft Ferrites

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process provided by spin rotations and domain walls and, on the other hand, the concept of loss separation. It additionally contemplates a distinction between the involved microscopic dissipation mechanisms: spin damping and eddy currents. Selected experimental results on the broadband behavior of complex permeability and losses in Mn-Zn ferrites provide significant examples of their dependence on sintering methods, solute elements, and working temperature. We also highlight the peculiar frequency and temperature response of Ni-Zn ferrites, which can be heavily affected by magnetic aftereffects. The physical modeling of the losses brings to light the role of the magnetic anisotropy and the way its magnitude distribution, affected by the internal demagnetizing fields, acts upon the magnetization process and its dependence on temperature and frequency. It is shown that the effective anisotropy governs the interplay of domain wall and rotational processes and their distinctive dissipation mechanisms, whose contributions are recognized in terms of different loss components.

Hydrothermal synthesis and microwave absorption properties of reduced graphene oxide/BaCo0.2Ti0.2Fe11.6 O19 nanocomposites

M-type barium hexaferrite with composition BaCo0.2Ti0.2Fe11.6 O19 was synthesized by sol-gel method and nanocomposites of Reduce Graphene Oxide/BaCo0.2Ti0.2Fe11.6O19 were also synthesized by hydrothermal method. The electromagnetic (EM) characteristics were studied in the frequency range of 2–18 GHz. The x-ray diffraction analysis confirms the formation of required nanocomposites and Scanning Electron Microscopy (SEM) analysis depicts the spherical morphology of BaCo0.2Ti0.2Fe11.6O19 (BCTF) nanoparticles, which are embedded in Reduce Graphene Oxide (RGO) sheets. The Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy confirm the purity of required phases. The Raman Spectra shows that ID/IG ratio increases from 0.967 to 1.379 for RGO/BCTF nanocomposites and produce defects in the sample. The magnetic properties were measured by vibrating sample magnetometer (VSM) in the magnetic field ranged from ±12,000 Oe. The RGO/BCTF transforms in to soft ferrite by the doping of Co2+ and Ti4+ cation in M-type hexagonal ferrite. The complex permittivity and permeability were measured by vector network analyzer in the frequency range of 2–18 GHz. The minimum Reflections Loss (RL) reached −18.24 dB for RGO/BCTF at frequency of 6.8 GHz with a thickness of 2 mm and also broadens the effective absorption bandwidth from 3.77 to 4.5 GHz. The effect of coating thickness (1–2 mm) transforms the absorption peaks towards higher frequency with decrease in matching thickness.

Synergistic effect of V2O5 and Bi2O3 on the grain boundary structure of high-frequency NiCuZn ferrite ceramics

High-frequency soft magnetic ferrite ceramics are desired in miniaturized and efficient power electronics but remain extremely challenging to deploy on account of the power loss (Pcv) at megahertz frequencies. Here, we prepared NiCuZn ferrite with superior high-frequency properties by V2O5 and Bi2O3 synergistic doping, which proves to be a potent pathway to reduce Pcv of the ferrite at megahertz frequencies. The sample doped with 800 ppm V2O5 and 800 ppm Bi2O3 yielded the most optimized magnetic properties with a Pcv of 113 kW/m3 (10 MHz, 5 mT, 25 °C), an initial permeability (μi) of 89, and a saturation induction (Bs) of 340 mT, which is at the forefront of the reported results. These outstanding properties are closely related to the notable grain boundary structure, which features a new type of nano-Bi2Fe4O9 phase around ferrite grains and a Ca/Si/V/O amorphous layer. Our results indicate great strides in correlating the grain boundary structure with multiple-ion doping and set the scene for the developing high-frequency soft magnet ferrites.

Observation of the magnetic entropy change in Zn doped MnFe2O4 common ceramic: Be cool being environmental friendly

We report the detail investigation on the magnetic and magnetocaloric behaviour of polycrystalline Mn1-xZnxFe2O4 (0.0 ≤ x ≤ 0.7) ferrite. The magnetization analysis shows that the increase of Zn concentration in the samples results in decrease of saturation magnetization. The maximum magnetic entropy change, |ΔSMmax| is evaluated through M-H isotherms measurements and takes values of 1.25, 1.11, 1.07, and 0.64 Jkg−1K−1 for x = 0.0, 0.3, 0.5, and 0.7, respectively under a maximum applied magnetic field of 2.5 T. The corresponding relative cooling power (RCP) for these samples were found to be 102, 162, 96, and 89 Jkg-1 for x = 0.0, 0.3, 0.5, and 0.7, respectively. After the comparison of the obtained values of |ΔSMmax| and RCP with those reported earlier for the other compounds, recommend to explore such common soft ferrites based materials for magnetic refrigeration.