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In response to the demands for high frequency, miniaturization, and high integration in electronic devices, such as inductors and DC-DC convertors, nickel–zinc ferrite thin films exhibit significant application value and development potential. For regulating the magnetic properties and microstructure of spin-sprayed polycrystalline ferrite materials, a comprehensive understanding of the impact of oxidant concentration on film reaction is essential. This study finds that as the concentration of the NaNO2 oxidant increases, the grain size of the nickel–zinc ferrite thin film samples progressively enlarges. Due to the preferential occupation of iron ions at the B sites, the saturation magnetization correspondingly increases. However, when the oxidant concentration becomes excessive, the preferential (222) orientation growth of the film is disrupted, leading to the agglomeration and uneven growth of grains, transitioning from triangular plate-like to spherical in shape. This increase in grain size alters the magnetization mechanism of the thin film, predominantly favoring domain wall movement. Upon analyzing the microstructure and magnetic characteristics, it becomes evident that the concentration of oxidant is a key determinant in the spin-spray deposition process. [ABSTRACT FROM AUTHOR]

Large effective magnetic anisotropy and low coercivity are usually mutually exclusive in nanometer crystalline ferrite due to opposing dependencies on the grain size. Here, by applying a parallel magnetic field during sputtering, NiZnCu ferrite thin films with larger effective magnetic anisotropy, as well as lower coercivity and an ideal permeability spectrum were prepared through adjustment of exchange length Lex. A (400) preferred orientation and a declined lattice constant triggered by the magnetic field were observed, and the cation redistribution was thoroughly discussed by XRD intensity calculation in which iron ions presented a tendency to occupy the octahedral site. By collective effects of grain growth promotion and enlarged anisotropy energy, the inducing magnetic field permitted samples with invariant stoichiometric composition a higher initial permeability and a broader working frequency range. These findings provide a valuable reference for effectively tuning magnetic properties of the magnetic thin films that are promising for high-frequency applications. [ABSTRACT FROM AUTHOR]

Manganese–zinc (MnZn) power ferrites own significant applications in inductors and transformers for power conversion. The performance of these components is dependent on permeability, saturation induction, core losses, and dc bias superposition characteristics of MnZn ferrites. It is worth emphasizing that excellent dc bias superposition characteristics of ferrites are beneficial for the stability and efficiency of power converters operated with both ac and dc signals. In this paper, Co2O3-doped MnZn ferrites are fabricated using a solid-state reaction method and used to investigate dc bias superposition characteristics of permeability and core losses. More importantly, the physical mechanism of the dc bias superposition characteristics is clarified. Furthermore, the effect of Co2O3 doping on the efficiency of buck circuit was also investigated. The dc bias superposition characteristics suggests potential application in power components and systems. [ABSTRACT FROM AUTHOR]

Manganese-zinc (MnZn) ferrites have important application in convertors and switching mode power supplies. The core losses ($\text{P}_{L}$) of MnZn ferrites have serious influence on the performance of power conversion devices. It is worth emphasizing that reducing the core losses at high frequency is of great significance for the miniaturization and integration of power conversion devices. Here in this paper, MnZn ferrites have been fabricated by the method of solid-state reaction, and the effect of CaCO3 and V2O5 co-additives on the microstructure and magnetic property has been investigated. This paper illustrated the competition mechanism of grain growth, which originated from the hindrance effect of CaCO3 and acceleration effect of V2O5, as well as the effect of CaCO3 and V2O5 on core losses by means of loss separation method. In addition, as for the MnZn ferrite sample with 0.1 wt% CaCO3 and 0.01 wt% V2O5 co-additives, core losses were suppressed to 46 and 664 kW/m3 corresponding to 3 MHz 10 mT and 3 MHz 30 mT at 25 °C, respectively. The state-of-the-art MnZn ferrites with ultralow core losses own potential application for high-frequency power conversion devices. [ABSTRACT FROM AUTHOR]

A low-loss Mn0.7Zn0.24Fe2.06O4 ferrite has been prepared by a solid-state reaction method. The MnZn ferrite has a high initial permeability, μi (3097), a high saturation induction, Bs (526 mT), a high Curie temperature, Tc (220 °C), and a low core loss, PL (≤ 415 kW/m3) in a wide temperature (25-120 °C) and frequency (10-100 kHz) range. As the temperature increases, an initial decrease followed by a subsequent increase of hysteresis loss, Ph, and eddy current loss, Pe is observed. Both Ph and Pe increase with increasing frequency. When f ≥ 300 kHz, a residual loss, Pr, appears. Pe increases with increasing temperature and frequency. The temperature and frequency dependence of Ph can be explained by irreversible domain wall movements, Pe by the skin effect, and Pr by domain wall resonance, respectively. [ABSTRACT FROM AUTHOR]

Polycrystalline ferrites Ni 0.5- x Cu 0.12 Zn 0.4 Co x Fe 1.98 O 4- δ with different cobalt-substituted contents ( x  = 0, 0.003, 0.006, 0.009, 0.012, 0.015) are synthetized via the solid-state reaction method. The magnetocrystalline anisotropy constant is calculated based on the law of approach to saturation. As the amount of cobalt substitution increases, the absolute value of the magnetocrystalline anisotropy constant first decreases and then rises due to the positive compensation by the Co 2+ ions. The value of the magnetocrystalline anisotropy constant tends to be zero for the samples with cobalt substitution contents in the range of 0.003–0.006. Meanwhile, when the cobalt substitution content is 0.003, the NiCuZn ferrite shows minimum ferromagnetic resonance linewidth (9.87 kA/m) and low dielectric loss tangent (tg δ ε , 1.1 × 10 −4 ) at 9.4 GHz as well as a high magnetization ( M s , 406 kA/m) and high squareness ratio ( B r / B s , 0.83). Furthermore, the linewidth contribution is identified by the anisotropy and porosity linewidth broadening model based on the spin-wave approach, and the results show that porosity linewidth broadening is the predominant effect. [ABSTRACT FROM AUTHOR]

Discussed is a novel self-biased hexaferrite gelling system based on a nontoxic and water-soluble copolymer of isobutylene and maleic anhydride. This copolymer simultaneously acts as a dispersant and gelling agent, and recently received much attention from the ceramics community. Herein its effects on the rheological conditions throughout magnetic-field pressing, and consequently, orientation, density and magnetic properties of textured hexaferrites were investigated. Ka-band FMR linewidths were measured, and the crystalline anisotropy and porosity induced linewidth broadening were estimated according to Schlömann’s theory. The copolymer allowed to reduce the friction between micron-sized magnetic particulates, resulting in higher density and degree of crystalline orientation, and lower FMR linewidth. [ABSTRACT FROM AUTHOR]

By adjusting the duration time of sintering, nickel–zinc (NiZn) ferrites with gradually varied grain sizes have been fabricated by the solid-state reaction method and their magnetization mechanisms and temperature dependence were investigated. In order to manifest the variation of permeability, the dominant magnetization mechanism was investigated by resolving the complex permeability spectra into two components including domain wall movement and spin rotation magnetization. The results show that, with grain size increasing, the dominant contribution to magnetization mechanism changes from spin rotation magnetization to domain wall movement due to the increase of amount of domain wall, and the amount of domain wall is observed by Lorentz microscopy to measure the critical diameter of magnetic domain which is around 3 μm in NiZn ferrite. The temperature dependence of the magnetization mechanism has been discussed for the sake of thermal stability. As the operating temperature increases, the ratio between two magnetization mechanism components appears to be stable around 4 after a shift from 1.76, and the domain wall movement totally dominates the variation of permeability as the main magnetization mechanism. [ABSTRACT FROM AUTHOR]

Ni 0.45 Zn 0.5 Mn 0.05 Fe 2 O 4 ferrite thin films (NZFs) were deposited on different substrates [Si(100), Si(111) and MgAl 2 O 4 (100)] by radio frequency (RF) magnetron sputtering method. The phase structure, surface morphology and magnetic property of NZFs were investigated using the X-ray diffractometer (XRD), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM), respectively. All the NZFs deposited on three kinds of substrates possess spinel structure, while only the film deposited on MgAl 2 O 4 (100) substrate [NZF/MgAl 2 O 4 (100)] has a preferred orientation along the direction of (100) because of the strong inducing effect of substrate. NZF/MgAl 2 O 4 (100) owns smoother surface than that of the film deposited on Si(111) substrate [NZF/Si(111)]. However, NZF/MgAl 2 O 4 (100) possesses larger grain size and much inhomogeneous distribution of grain size than that of NZF/Si(111). NZF/MgAl 2 O 4 (100) has the greatest saturation magnetization ( M s ) of 345 kA/m and coercivity ( H c ) of 5.80 kA/m. According to the stress model, the coercivity of NZFs deposited on various substrates has been calculated and discussed, which matches with the experiment results. [ABSTRACT FROM AUTHOR]

Ni-substituted manganese–zinc (MnZn) ferrites with the composition of Mn0.506–xZn0.244NixFe2.250O4.0 ( x = 0.066\sim0.122 ) have been prepared by the solid-state reaction method. The cation distribution has been investigated by the Rietveld refinement of X-ray diffraction patterns, the microstructure has been observed using a scanning electron microscope, and the magnetic property has been measured using superconductor quantum interference devices and B – H analyzer. The results show that Zn2+ and Ni2+ ions prefer to occupy the tetrahedron site (A sublattice) and octahedron site (B sublattice), respectively. However, Mn2+ and Fe3+ ions can enter into A and B sublattices, where the ratio of Mn2+ ions occupying A and B sublattices is 4:1. The lattice parameter ( a ) of the samples decreases with the increase of Ni-substituted content. Meanwhile, based on the Néel model of collinear-spin ferrimagnetism, the molecular-field coefficients , \omega _{\rm BB} , and \omega _{\rm AB} of the Ni-substituted MnZn ferrites have been calculated, and the magnetic moment of A and B sublattices versus temperature T has also been investigated. The fitting results match well with the experimental data. Both \omega _{\rm AB} and \omega _{\rm BB}$ increase with the increase of the Ni-substituted content, but \omega _{\rm AA} shows the opposite variation trend. The Curie temperature also increases with the increasing of the Ni-substituted content, which is attributed to the enhancement of superexchange interaction for A–B sublattice. In addition, the temperature dependence of initial permeability and core loss has been discussed. [ABSTRACT FROM AUTHOR]

NiZn ferrites with different amounts of CuO have been synthesized by the conventional ceramic method and their spectra of complex permeability were investigated. The CuO contents affect the grain size and microstructure of NiZn ferrite obviously, which also result in the variation of saturation magnetization, magnetocrystalline anisotropy, and porosity. Along with these relevant magnetic properties, the superposition of magnetizing mechanisms was testified to be predominant in determining the value of permeability. To manifest the increase of initial permeability, the permeability spectra of NiZn ferrite were resolved into two components, including domain wall movement and spin rotation magnetization. The fitting results show that, with the increasing amounts of CuO, the dominant contribution to dynamic magnetization changes from spin rotation magnetization mechanism to domain wall movement. [ABSTRACT FROM AUTHOR]

NiMgCuZn ferrites co-doped with Ta 2 O 5 and Co 2 O 3 additives have been prepared by a solid-state reaction method. The influence of Ta 2 O 5 –Co 2 O 3 (TC) additives on the microstructure, static magnetic properties and core losses ( P cv ) at high frequency of NiMgCuZn ferrites has been investigated by scanning electron microscope (SEM), LCR meter and B–H analyzer. The results revealed that the composite additives reduce the sintering density via inhibiting the grain growth. According to Zagg’s report, the average grain sizes are smaller than 2.4 μm for different TC contents, hence all the samples have single domain structures. In addition, the saturation induction and initial permeability of the samples reduce monotonously with the increase of TC contents. While the coercivity and cutoff frequency show an opposite trend. For the samples with different TC contents, the core losses at high frequency have been discussed. [ABSTRACT FROM AUTHOR]

Barium hexaferrites BaFe12O19 with Bi2O3/CuO additives were synthesized by the conventional oxide ceramic process. The results manifest that Bi2O3 additives mainly concentrate on the grain boundary regions, while CuO additives could both enter into the grain and segregate at the grain boundary regions. The appropriate sintering temperature of barium hexaferrites with Bi2O3 and Bi2O3 + CuO additives reaches 1020 °C and 920 °C, respectively. As the amount of Bi2O3 is 3 wt%, the specimens of BaFe12O19 show saturation magnetization (Ms) of 346 kA/m, remanence (Mr) of 227 kA/m, and density (d) of 5.06 g/cm3. Meanwhile, the combination of 3 wt% Bi2O3 and 3 wt% CuO additives significantly promotes grain growth and sintering densification, with a high saturation magnetization of 371 kA/m and density of 5.23 g/cm3 for BaFe12O19, which are pretty close to the theoretical values (380 kA/m, 5.28 g/cm3). Moreover, the corresponding remanence could also rise by 10% compared with that in the sintered samples with 3 wt% Bi2O3. [ABSTRACT FROM AUTHOR]

The effects of \ Bi2{\ {O}}3 on dispersion spectra of permeability and permittivity for LiZnMn ferrite prepared by a conventional ceramic method were investigated. Optimum content of \ Bi2{\ {O}}3 can obviously affect the permeability and permittivity of LiZnMn ferrite via promoting grain growth and densification. The permeability spectra of LiZnMn ferrite were resolved into two contribution components, domain wall movement and spin rotation magnetization. The fitting results manifest that, with \ Bi2{\ {O}}3 concentration increasing, the major contribution to dynamic magnetization changes from spin rotation magnetization mechanism to domain wall movement, and the domain wall spectra change from resonance-type to relaxation-type, but the spin rotation spectra behave in the opposite way. Meanwhile, the mechanism of dielectric polarization and dielectric loss of the samples were discussed. [ABSTRACT FROM AUTHOR]

M-type barium ferrite (BaM) thin films with two different structures (single layered and double layered) were deposited on thermally oxidized silicon (SiO2/Si) substrates by radio frequency (RF) magnetron sputtering. The changes in surface morphologies, crystallographic and magnetic properties of the films corresponding to different structures and substrate temperatures (Ts) were investigated in detail. In the single layered films deposited directly on SiO2/Si substrates at Ts= 300\,\,^{\circ}C and Ts = 500\,\,^\circC respectively, most of the grains are acicular type. XRD data and magnetic properties measurement confirmed that they are both weakly c-axis perpendicularly oriented. However, in the double layered film with first interfacial layer deposited at Ts= 300\,\,^\circC and second layer deposited at Ts= 500\,\,^\circC, good crystallographic characteristics and excellent perpendicular c-axis orientation were obtained. The c-axis dispersion angle (\Delta \thetac) decreased to 0.51\,\,^\circC; the lattice parameters were comparable to those of the bulk BaM; the squareness ratio and coercivity of the out-of-plane increased to 0.85 and 338 kA/m, respectively, for the double layered film. The mechanism for improving perpendicular c-axis orientation with an interfacial BaM layer was attributed to two reasons. One is a relative increase in the nucleation sites for perpendicularly oriented grains over the nucleation sites for in-plane and/or randomly oriented grains, and the other is the release of stress that comes from the interface between BaM thin film and SiO2/Si substrate. [ABSTRACT FROM AUTHOR]

Abstract: Polyethylene glycol (PEG) modified Ni0.5Zn0.5Fe2.0O4.0 ferrite thin films were deposited on Si (100) substrate by a sol–gel method. The crystal structure, surface morphology and magnetic properties of PEG-modified NiZn ferrite thin films (NZFs) were investigated by using the X-ray diffractometer (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The FTIR spectrums showed that PEG molecules were on the surface of as-prepared particles, which effectively improved their dispersibility. The crystallization of NZFs improved and crystallite size increased with increasing PEG concentration. Optimal PEG concentration could improve the surface morphology and reduce the roughness. Magnetic properties measurement indicated that compared with the sample without PEG, PEG-modified NZFs showed excellent magnetic properties with higher saturation magnetization and lower coercive force. Finally, PEG-modified NZFs showed a high saturation magnetization 312 emu/cm3 and low coercive force 90 Oe when PEG concentration was 40 g/L. [Copyright &y& Elsevier]

Abstract: We studied the effects of iron-deficient, stoichiometric and iron-excessive compositions on the phase formation, crystal structure, grain growth and magnetic property of NiCuZn ferrites. As the Fe2O3 ratio increased from iron-deficiency 47.0mol% to iron-excess 54.0mol%, the X-ray diffraction peaks initially shifted towards lower angle and then moved to higher angle. Correspondingly, an initial increase in lattice parameter followed by a subsequent decrease was observed. The lattice parameter showed a maximum 8.396Å when the Fe2O3 ratio was 49.0mol%. When the system was iron-deficient, ZnO phase was detected in addition to the spinel phase. However, equimolar and iron-excessive compositions exhibited a single spinel phase. As the content of Fe2O3 increased, the grain size, density, saturation induction and initial permeability first increased and then decreased. Core losses at 50kHz and 150mT, however, changed in the opposite way. Finally, NiCuZn ferrite with an equimolar composition (50.0mol%) showed the highest initial permeability (1467), highest saturation induction (361mT) and lowest core losses (234kW/m3). [ABSTRACT FROM AUTHOR]

Abstract: The core losses (PL ) of MnZn ferrites prepared by a solid-state reaction method were investigated as a function of magnetic induction and frequency (). The exponent (x) of magnetic induction was 2.58 at 1000kHz and 2.01 at 3000kHz, and the exponent (y) of frequency was 2.22 at 30mT and 2.73 at 10mT. The core losses (PL ) were divided into hysteresis loss (Ph ), eddy current loss (Pe ) and residual loss (Pr ). Each loss contribution was discussed to be dependent on temperature. Ph decreased monotonically with increasing temperature. Pe firstly decreased with increasing temperature, minimized at 100°C, and then increased. As the temperature increased, the imaginary permeability at MHz was significantly enhanced and the resonance frequency (fr ) decreased. The increase in Pr with increasing temperature should be attributed to the decreasing fr which is due to the resonance in the domain wall caused by high speed rotation of spin inside the domain. [Copyright &y& Elsevier]

Abstract: Structural, microstructural and electromagnetic properties of NiO doped manganese–zinc (MnZn) ferrites prepared by a solid-state reaction method have been investigated. The continuous doping of NiO resulted in an increase in lattice constant (a), porosity (P) and electrical resistivity (ρ), a decrease in average grain size (D) and bulk density (d b), while no obvious change in X-ray density (d X). Hysteresis loss (P h) increased monotonically with increasing NiO, and its variation could be explained by the relation: , where μ i was initial permeability. Eddy current loss (P e) first reduced before achieving its minimum, and then rose gradually. The variation of P e was inconsistent with the classical expression, P e,cl ∝ D 2/ρ, where D and ρ were average grain size and resistivity, respectively, and the excess loss (P e,exc) could contribute to the P e. Residual loss (P r) reduced slowly due to D’s decrease and f r’s increase which were caused by the increase in NiO, where f r was resonance frequency. Finally, the sample doped with 0.10wt% NiO showed the lowest losses of 207kWm−3 at 100°C, 1MHz and 30mT. [Copyright &y& Elsevier]

Abstract: Manganese–zinc (MnZn) ferrites doped with NiO addition were prepared by solid-state reaction method. Losses (P L) were divided into hysteresis loss (P h), eddy current loss (P e) and residual loss (P r), temperature and frequency characteristics of each loss, and the ratio of each loss to the total losses have been discussed. P h increased monotonously with increasing NiO, and its variation can be explained by the relation: . P e first reduced before achieving its minimum, and then rose gradually. The variation of P e was not consistent with the classical expression, P e,cl ∝ D 2/ρ, with D as grain size, and the excess loss (P e,exc) can contribute to the P e. P r decreased gradually with increasing NiO due to D''s decrease and fr''s increase, with fr as resonance frequency. Finally, the sample doped with 0.10wt.% NiO showed the lowest losses of 175kW/m3 at 100°C, 0.5MHz and 50mT, and of 207kW/m3 at 100°C, 1MHz and 30mT. [Copyright &y& Elsevier]

Abstract: The microstructure and magnetic properties of SnO2-doped NiZn ferrites prepared by a solid-state reaction method have been investigated. Due to its low melting point (∼1127°C), moderate SnO2 enhanced mass transfer and sintering by forming liquid phase, which accelerated the grain growth. However, excessive SnO2 producing much of liquid phase retarded mass transfer and sintering, leading to a decrease in grain size. The diffraction intensity of the samples doped with SnO2 addition was stronger than that of the sample without addition. The lattice constant initially decreased up to a content of 0.10wt% and showed an increase at higher content up to 0.50wt%. The initial permeability (μ i) initially increased up to a content of 0.15wt% and showed a decrease at higher content up to 0.50wt%; however, losses (P L) measured at 50kHz and 150mT changed contrarily. Both saturation induction (B S) and Curie temperature (T C) decreased gradually with increasing SnO2. Finally, the sample doped with 0.10–0.15wt% SnO2 showed the higher permeability and lower losses. [Copyright &y& Elsevier]

Abstract: Sn-substituted NiZn ferrite thin films, Ni0.5+ x Sn x Zn0.5Fe2−2 x O4 (0⩽x⩽0.2), were synthesized by a sol–gel method. The crystallographic and magnetic properties of Ni0.5+ x Sn x Zn0.5Fe2−2 x O4 thin films have been investigated. The diffraction peak shifted towards the lower angle and the lattice parameter increased with Sn substitution. Both grain size and surface roughness of the thin films with Sn substitution were bigger than those of the film without substitution. Hysteresis loops of thin films demonstrated that the Sn-substituted films were more easily saturated than that of the film without substitution. Saturation magnetization (Ms) of thin films decreased with increasing Sn substitution, however, coercivity (Hc) changed contrarily. [Copyright &y& Elsevier]

Although substrate wettability greatly impacts deposition processes using the spin-spray technique, there are few substrates suitable for the deposition of spin-sprayed ferrite thin films. To tune substrate wettability without changing the type of substrate, we demonstrate a Ni 0.17 Zn 0.52 Fe 2.31 O 4 ferrite film deposited by the spin-spray technique on a 0.2 mm glass substrate with 0–5% aqueous ethanol solutions. All samples showed (222) preferential orientation and triangular grain morphology. The effects of aqueous ethanol solutions on the microstructure and magnetic properties of ferrite thin films were also investigated. When the ethanol volume percent concentration equaled 3%, the columnar morphology of the microstructure was most evident and the saturation magnetization and the real permeability reached their maximum values. Because of the shape anisotropy of the columnar structure, the coercivity of the parallel magnetic field increased, whereas the coercivity of the perpendicular magnetic field decreased. First-order inversion curve measurements revealed that ethanol-containing ferrite thin films had a more uniform grain size. [ABSTRACT FROM AUTHOR]

Traditional circulators utilize ferrites with low magnetocrystalline anisotropy driven by external magnetic bias fields. Hexagonal ferrites with a strong uniaxial anisotropy enable self-biased circulators, significantly reducing their volume, weight, and cost. Here, a unique uniaxial hexaferrite, Cu 18H hexaferrite, with narrow ferrimagnetic resonance (FMR) linewidth at zero magnetic bias field is reported. The temperature-dependent magnetic hysteresis loops show a significant decrease in coercivity from cryogenic to room temperature, indicating a transition from the hard to soft magnetic state. The crystallographic texture ensures a squareness ratio greater than 0.65 and leads to a strong internal bias field induced by the aligned easy-magnetization axes. Owing to the highly dense and oriented crystallites, the zero-field FMR exhibits excellent linewidths of ∼270–320 Oe, which are lower than those of most hexaferrites reported at the K a -band. These results reveal the great potential of Cu 18H hexaferrite as a low-loss microwave ferrite used for self-biased circulators. [ABSTRACT FROM AUTHOR]

While the Cu substitution in NiCuZn ferrites is known to enhance densification and increase the initial permeability (μ i), little is known about its effects in the MnZn based ferrites, which naturally possess a higher saturation magnetization (M s) and μ i. In this study, the effects of Cu substitution for Mn on the power MnZn ferrites (Mn 0.71-x Cu x Zn 0.22 Fe 2.07 O 4 , x = 0.00–0.35) are investigated. With increasing Cu content, enhanced density, reduced porosity, and significant grain growth are observed. The cation distribution was determined using the Rietveld refinement, showing the strong tendency of Cu2+ ions to occupy the octahedral sites of the spinel lattice. The magnetization curves show reduced M s with increasing Cu content. The magnetic anisotropy (| K |) was also determined from the magnetization curves using the law of approach to saturation and is seen to be increased by the increasing Cu content. The reduced M s and increased | K | lead to the dramatic reduction of μ i from 2503 (x = 0.00) to 151 (x = 0.35) at room temperature. Despite the reduced M s at room temperature, the Curie temperature (T C) is seen to increase with increasing Cu content from x = 0.05 to x = 0.35, indicating the relocation of cations at an elevated temperature. The cut-off frequency (f r) is increased with increasing Cu content, which corresponds to the reduced μ i. Moreover, the core loss (P cv) of the MnCuZn ferrites was tested at 100kHz/200 mT, 200kHz/125 mT, and 300kHz/100 mT at room temperature, and is found to deteriorate with the increasing Cu content. [ABSTRACT FROM AUTHOR]

Nickel-zinc ferrite (NZF) discs and magnesium calcium titanite (MCT) dielectric ceramic discs were laminated and co-fired to prepare NZF/MCT bi-layer laminated heterostructure samples. The sintering shrinkage of NZF and MCT was matched well via adjusting the sintering temperature. Ion diffusion curves at the co-fired joint interface were derived by electron-probe microanalysis (EPMA) and fitted basing on infinite diffusion coupling model. Ion diffusion mechanism at the co-fired joint interface was investigated in detail. The results show that Zn2+ ions have the highest diffusion coefficient because of the smaller ion radius which is benefit for interstitial diffusion, while Ca2+ ions have the lowest diffusion coefficient and segregate along the interface of MCT side. Fe3+ ions have the biggest diffusion width because of the interstitial diffusion in the incompletely densified MCT. Sintered at 1260 °C, the maximum interdiffusion width is narrow to be about 102 μm. With increasing temperature, ion diffusion coefficient and diffusion distance both go up obviously. • Nickel-zinc ferrite (NZF) discs and magnesium calcium titanate (MCT) dielectric ceramic discs were co-fired to prepare heterostructure samples. • The microscopic morphology and EDS mappings near the interface of NZF/MCT were observed and identified, respectively. • Cations concentration curves were derived by EPMA and fitted. The diffusion width and diffusion coefficient were determined. • The ion diffusion mechanisms at co-fired joint interface were investigated in detail. [ABSTRACT FROM AUTHOR]

With the increasing power density of the switched mode power supply (SMPS) developed nowadays, higher efficiency is required from the magnetic core, where the MnZn ferrites are often adopted. However, the relatively high operating temperature of the SMPS often results in reduced resistivity of the MnZn, which increases the eddy current loss. To enhance the resistivity of MnZn ferrite at high temperature range (>100 °C), donor-doped barium strontium titanate (BST) with a positive temperature coefficient of resistivity (PTCR) is prepared and dopped in the MnZn ferrite. The influence of BST addition from 0.000 wt% to 0.020 wt% on the MnZn ferrite is investigated over a wide temperature range from 25 °C to 140 °C. The XRD result suggests ionic exchange between the spinel phase and perovskite phase. The SEM result shows a refined and more uniform microstructure of MnZn ferrite brought about by the BST addition. At the maximum of 0.020 wt%, the BST addition shows almost no influence on density and the saturation magnetic induction. However, the initial permeability is slightly reduced by the BST addition, due to the microstructural change. Moreover, the BST concentrating at the grain boundaries improves the DC-resistivity across the temperature range from 25 °C to 140 °C. Due to the addition of BST, the reduction in eddy current loss at 300kHz/100 mT is around 35% at 25 °C, and ∼20% reduction at 140 °C. [ABSTRACT FROM AUTHOR]

Grain size plays an important role in affecting the physical properties of ceramics. In this work, the effects of pre-sintering grain size G 0 of BaFe 12 O 19 (BaM) on the microstructure and magnetic properties of hot-press sintered BaM thick films were studied. Results show that reducing G 0 in submicron scale leads to notable decreases in grain growth activation energy and final sintered grain size. Smaller G 0 makes BaM grains easier to be aligned by magnetic field before sintering and less magnetic domain walls in the sintered film. This increases the c -axis orientation, out-of-plane remanence ratio SQ (>0.9) and coercivity of sintered film. Moreover, the zero-field ferromagnetic resonance linewidth ΔH decreases 54% as G 0 reduces from 1 μm to 0.3 μm. This is attributed to the increased film uniformity with larger SQ and film density D rel at smaller G 0. The above findings enable better understanding on the role of G 0 in improving the magnetic properties of hot-press sintered BaM and other hexaferrite thick films for self-biased microwave devices. [ABSTRACT FROM AUTHOR]

Abstract: M-type Ba-hexaferrite (BaM) thin films with different thicknesses were deposited on (001) Al2O3 substrates by RF magnetron sputtering. Effects of film thickness on the crystallographic, morphological and magnetic properties were investigated. Experimental results showed that properties of BaM thin films are strongly dependent on thickness and thinner film favors to obtain better (00 l) planes orientation with narrower XRD FWHM. The 150-nm thick film possesses columnar-type grains having c-axis orientation perpendicular to the film plane. However, with the thickness increasing from 150 to 550nm, acicular-type grain increases. Thus, the texture of (00 l) planes orientation of the film deteriorates; the saturation magnetization and perpendicular magnetocrystalline anisotropy also decrease gradually. Mechanisms for these variations are attributed to the increase of random nucleation sites and strain relaxation in the films with increasing thickness. [Copyright &y& Elsevier]

Abstract: This paper focuses on the grain growth kinetics described by tradition phenomenological rate equation through nonlinear fitting of grain sizes for Ni0.5Zn0.5Fe2O4 ferrite thin films. The grain growth exponent n, which matches with normal grain growth, equals to 2.43 at 600°C, and the process is controlled by anomalous solute drag which effects on the grain boundary mobility. As the annealing temperature rises from 700°C to 900°C, correspondingly the n goes up from 3 to 4, indicating that volume diffusion happens. The activation energy for grain growth are 22.75, 42.52, 56.32 and 85.54kJ/mol from 600°C to 900°C, respectively, they are much smaller than that of the NiZn ferrite bulk. The effects of annealing temperature on the magnetic properties, phase structure and microstructure are investigated. The coercivity of NiZn ferrite thin films is mainly discussed via stress model. [Copyright &y& Elsevier]

Abstract: Sn-substituted MnZn ferrites were prepared by conventional oxide ceramic process. The influences of Sn substitution on microstructure and magnetic properties of MnZn ferrites were investigated. The results indicated that with increase of Sn substitute concentration, the diffraction peaks shifted slightly towards the lower angles and the lattice parameter (a) increased. And at room temperature, the bulk density (d m), initial permeability (μ i), saturation magnetic induction (B s) and electrical resistivity (ρ) of Sn-substituted MnZn ferrites all increased initially and then decreased with the further increase of Sn substitute concentration, while the power losses decreased first and then increased subsequently. Meanwhile, the temperature of secondary maximum peak of μ i–T curve and the minimum losses moved to lower temperature while the Sn substitute concentration increased. When the content of Sn substitution was 0.3mol%, at room temperature, the initial permeability, saturation magnetic induction, density and electrical resistivity reached their maxima, while the hysteresis loss (P h), eddy current loss (P e) and total losses (P cv) achieved their minima. The P h∼T and μ i–T curves varied contrarily, and due to the contribution of extra eddy current loss (P e,exc) that was proportional to P h, the P e–T curve did not agree with its classical expression. Finally, MnZn ferrite substituted with 0.3mol% SnO2 shows the highest initial permeability (3894) and lowest losses (303kW/m3) at room temperature. [Copyright &y& Elsevier]

M-type Sr (SrM) hexaferrites have been widely applied in millimetre/microwave ferrite devices such as circulators and isolators. SrM hexaferrites must exhibit a high remanence ratio M r / M s , a high anisotropy field H a , and a low ferromagnetic resonance (FMR) linewidth Δ H to further develop millimetre/microwave equipment and devices with high frequencies, miniaturisation, and planarisation. However, it is difficult for M-type hexaferrite to simultaneously meet the requirements of high M r / M s , high H a , and low Δ H , which are key to realising high-frequency self-biased ferrite devices. In this work, Ca–La–Co-substituted SrM ferrite was prepared, and the influence of La substitution on the micromorphology, static magnetic properties, and Δ H values of SrM hexaferrites is discussed in detail. The results demonstrated that as the La substitution content x increased from 0.0 to 0.5, the saturation magnetisation 4π M s and coercivity H c initially increased, and then decreased. The H a values of all samples were higher than 18 kOe. The FMR linewidth Δ H initially increases, and then decreased after reaching a maximum value at x = 0.2. The independent grain approximation theory was used to analyse the changing trend of the FMR linewidth. The results showed that the crystalline anisotropy linewidth Δ H a accounted for a larger proportion of the FMR linewidth than the porosity linewidth Δ H p. The sample with a La substitution content x of 0.3, exhibited the best performance (4π M s = 3915 Gs, 4π M r = 3387 Gs, H c = 1818 Oe, M r / M s = 0.865, large H a = 23.99 kOe, and Δ H = 1548 Oe at 58.8 GHz). The materials prepared in this research have significant potential for application in high-frequency self-biased devices and microwave engineering. [ABSTRACT FROM AUTHOR]

Cancers are fatal diseases that lead to most death of human beings, which urgently require effective treatments methods. Hyperthermia therapy employs magnetic nanoparticles (MNPs) as heating medium under external alternating magnetic field. Among various MNPs, ferrite nanoparticles (FNPs) have gained significant attention for hyperthermia therapy due to their exceptional magnetic properties, high stability, favorable biological compatibility, and low toxicity. The utilization of FNPs holds immense potential for enhancing the effectiveness of hyperthermia therapy. The main hurdle for hyperthermia treatment includes optimizing the heat generation capacity of FNPs and controlling the local temperature of tumor region. This review aims to comprehensively evaluate the magnetic hyperthermia treatment (MHT) of FNPs, which is accomplished by elucidating the underlying mechanism of heat generation and identifying influential factors. Based upon fundamental understanding of hyperthermia of FNPs, valuable insights will be provided for developing efficient nanoplatforms with enhanced accuracy and magnetothermal properties. Additionally, we will also survey current research focuses on modulating FNPs' properties, external conditions for MHT, novel technical methods, and recent clinical findings. Finally, current challenges in MHT with FNPs will be discussed while prospecting future directions. [Display omitted] • Design of effective thermal media in magnetothermal therapy based on FNPs. • Several factors influencing the magnetothermal therapy of FNPs. • Recent pre-clinical works and challenges of cancer therapy by magnetic hyperthermia. • Combination of MTH with multi-modal therapeutic strategies for cancer therapy. [ABSTRACT FROM AUTHOR]

NiZn ferrite thin films with different compositions were prepared by spin spray deposition on an enhanced ultrasonic system and significant improvements in microstructure and magnetic properties of spin-sprayed thin-films were observed and explained. The formation of triangular grain morphology as a result of anisotropic growth was discussed based on a thin-film growth mechanism, and the preferred (222) anisotropic growth was deduced as the consequence of a uniform, fast-rate deposition of high-quality ferrite thin film by spin spray. First-order reversal curve measurement was adopted to investigate the grain size distribution of the abnormal microstructure. Moreover, a transition of magnetization mechanism took place along the increment of iron concentration which resulted in a larger permeability at high frequency. These findings provide a valuable reference for an in-depth understanding of spin spray deposition and an effective way to tune the performance of ferrite thin-film material. [ABSTRACT FROM AUTHOR]

The miniaturization and integration of power conversion devices and components, such as converters and switching power supplies, require ferrite cores with high operating frequencies and temperatures. Hence, the frequency and temperature dependence of core losses is a bottleneck restricting the development of power conversion devices. Herein, nanoparticles of a dielectric material—barium titanate (BTO)—are adopted to suppress high-frequency and high-temperature core losses in MnZn ferrites. Using a loss separation method, the effects of BTO on core losses and their temperature dependence are investigated. Residual loss at 25 °C and eddy current loss at high temperatures were significantly suppressed by the addition of BTO. Remarkably, adding 0.04 wt% BTO nanoparticles resulted in MnZn ferrites with ultra-low core losses of 302 kW/m3 (25 °C) and 890 kW/m3 (100 °C) at 3 MHz and 30 mT. These superior MnZn ferrites with ultra-low core losses have potential applications in power conversion devices with high operating frequencies and temperatures. This study also provides a novel approach for suppressing core losses. • BaTiO 3 nanoparticles additives can greatly suppress P L of MnZn ferrites. • Grains of MnZn ferrites are refined when BaTiO 3 is doped. • The suppression of P L at room temperature is affected by microstructure and P r. • The reduction of P L at high temperatures is attributed to the resistivity and P e. [ABSTRACT FROM AUTHOR]

Traditional Li-based and Ni-based spinel microwave ferrites have triggered tremendous interests, due to the excellent squareness B r / B s and high Curie temperature T c of Li-based ferrites, and low ferromagnetic resonance FMR linewidth Δ H and low coercivity H c of Ni-based ferrites, respectively. However, to meet the requirement of excellent temperature stability and low insertion loss of microwave/millimeter devices and components, the challenges remain to compromise the contradiction between Δ H and T c for traditional spinel microwave ferrites such as low Δ H and high T c. In order to make a breakthrough, herein, we explore introduce NiCuZn (NCZ) ferrites to LiZn (LZ) ferrites to synthetize a facile material LZ/NCZ composite microwave ferrites. The ions diffusion, static magnetic properties, Δ H and microwave dielectric performances have been systematically investigated. With the increase of sintering temperature from 800 °C to 1200 °C, the LZ/NCZ composite ferrites transfer from independent NCZ and LZ ferrites to homogeneity LNCZ ferrites. It is confirmed that the Δ H (247Oe ∼ 163Oe) and T c (403 °C∼332 °C) of LZ/NCZ ferrites can be tunable and are directly determined by the NCZ doping contents (0 wt% ∼ 100 wt%). The sample with 40 wt% NCZ possesses optimum comprehensive performance with high saturation magnetization (M s , 401 kA/m), high remanence (B r , 365 mT), high Curie temperature (T c , 367 °C), low coercivity (H c , 78A/m), low dielectric loss (tan δ , 2.61 × 10−4), and relative low FMR linewidth (Δ H , 207Oe). The state-of-the-art of LZ/NCZ composite ferrites with promising magnetic and electrical performances exhibit great potential for phase array radar systems operating in wide temperature range. • It is confirmed that the LZ/NCZ ferrites transfer from independent NCZ and LZ ferrites to homogeneity LNCZ ferrites. • The FMR linewidth Δ H and T c of LZ ferrite can be tunable and are directly determined by the NCZ doping contents. • The sample possesses optimum performance with M s (401kA/m), B r (365 mT), T c (367℃), tan δ (2.61×10−4), and low Δ H (207Oe). [ABSTRACT FROM AUTHOR]

• HfO 2 additive could improve microstructure and enhance DC resistivity ρ. • P h is reflected by the area of hysteresis loops (B - H). • P e is affected by the combined action of microstructure and DC resistivity ρ. Core losses in manganese-zinc (MnZn) ferrites is an important factor governing the performances of power conversion devices such as power converters and switching mode power supplies. With the development trend of miniaturization, lightweight, and high frequency for power supply, it is worth emphasizing that the temperature characteristics of ferrite cores are closely related to energy transfer efficiency and reliability of power conversion devices and components. Herein, the effect of high valence ion additive HfO 2 on the microstructure and electromagnetic performances of MnZn ferrites was systematically discussed, as well as physical mechanism of temperature dependence of core losses. The variation of hysteresis loss has been correlated with the hysteresis loop area (B-H), and the effect of the ratio of square of average grain size to resistivity D 2/ ρ on eddy current loss has been taken into consideration. Remarkably, eddy current loss does not monotonically decrease with the increase of HfO 2 content via enhancing resistivity ρ , as well with the variation of average grain size D. The state-of-the-art MnZn ferrites with excellent temperature characteristics of core losses exhibits great potential in power conversion devices operating in a wide temperature range. [ABSTRACT FROM AUTHOR]

NiCuZn (NCZ) ferrites have been widely used in non-reciprocal microwave/millimeter ferrite devices, such as circulators. With the development of microwave/millimeter devices and components to high frequency, miniaturization, and lightweight applications, NCZ ferrites have needed to satisfy the essential requirements of high saturation magnetization 4π M s , low coercivity H c , and low ferromagnetic resonance (FMR) linewidth Δ H. Herein, 0.1 wt% Bi 2 O 3 and 0.0–3.5 wt% CaCu 3 Ti 4 O 12 (CCTO) composite additives were introduced to NCZ ferrites, the influence of Bi 2 O 3 –CCTO composite additives on micromorphology, static magnetic properties, and FMR linewidth Δ H of NCZ ferrites have been demonstrated in detail. The results show that increasing the CCTO amounts in NCZ ferrites, saturation magnetization 4π M s monotonically decreases from 5484Gs to 4819Gs, and both coercive force H c and FMR linewidth Δ H first decreases and then increases with minimums of 31A/m and 147Oe, respectively. In addition, the theory of spin-wave narrowing and the law of approach to saturation have been adopted for the separation calculation of FMR linewidth Δ H to the crystalline anisotropy linewidth Δ H a and porosity induced linewidth Δ H p. The sample with 0.1 wt% Bi 2 O 3 and 1.5 wt% CCTO possesses high saturation magnetization 4π M s (5321Gs), remanence B r (200 mT), low coercivity H c (31A/m), and low FMR linewidth Δ H (147Oe). The state-of-the-art NCZ ferrites with outstanding performances manifest significant applied potency for microwave/millimeter devices and components in phase array radar systems. [ABSTRACT FROM AUTHOR]

Yttrium iron garnet (YIG) ferrites own significant applications in microwave magnetic devices, such as circulators, isolators and filters. The excellent performance and reliability of these devices are strongly dependent on the saturation magnetization ( M s ), ferromagnetic resonance (FMR) linewidth (Δ H ), dielectric loss tangent (tan δ ε ) and Curie temperature ( T c ) of the garnet ferrites. Here, we fabricate Ca-Sn co-substituted Y 3- x Ca x Fe 5- x Sn x O 12 ( x  = 0.0, 0.1, 0.2, 0.3 and 0.4) ferrites using solid-state reaction method, and investigate the thermomagnetization characteristics of Brillouin function and FMR linewidth based on Néel model of ferrimagnetism and spin wave approach, respectively. This study clarifies the intrasublattice molecular-field coefficients ω aa , ω dd and intersublattice coefficients ω ad =  ω da . More importantly, we propose an accurate formula of Curie temperature T c for garnet ferrites. Furthermore, Ca-Sn co-substitution can tailor the FMR linewidth based on the adjustment of anisotropy and the realization of densification. Finally, Y 2.7 Ca 0.3 Fe 4.7 Sn 0.3 O 12 ferrite exhibits optimized magnetic property: 4π M s = 2073 Gs, Δ H = 42 Oe, T c = 491 K. [ABSTRACT FROM AUTHOR]

Manganese-zinc (MnZn) ferrites play an indispensable role in energy transform and harvesting. It is notable to mention that the combined enhancement of initial permeability (μ i), saturation magnetic induction (B s) and Curie temperature (T c) is conducive to improving the output power and safety of magnetic field energy harvesting devices. In this paper, high permeability MnZn ferrites were synthesized by a conventional oxide ceramic method. The thermomagnetic curves of MnZn ferrites were fitted according to the Néel molecular field theory (NMFT) and the Brillouin function. Then the molecular field coefficient γ aa , γ ab , γ bb , and T c were calculated. Aiming at the magnetization mechanism of permeability, the contributions of domain wall motion and spin rotation were analyzed by fitting the complex permeability spectrum. Furthermore, the temperature characteristics of μ i and B s are analyzed, and we simulated and compared the effect of different magnetic properties of MnZn ferrites on the output of non-invasive magnetic field harvester. The MnZn ferrites with superior comprehensive performance own potential applications for non-invasive magnetic field harvester. • MnZn ferrite with excellent overall performance (μ i > 9000, B s ≈ 500mT, T c = 447 K) was prepared. • The principles of the molecular field coefficients were clarified by Brillouin function temperature characteristics. • The magnetization mechanism of Mn-Zn ferrite was elucidated by separation and fitting of the permeability spectrum. [ABSTRACT FROM AUTHOR]

The total energies and forces of the Ba 0.5 La 0.5 Fe 11.5 Cu 0.5 O 19 structure were calculated using the density functional theory (DFT) and generalized gradient approximation (GGA). The calculations demonstrated that at 0 K, the magnetic ions Cu 2+ preferentially occupy Fe 3+ at the 4 f 2 (0) and 4 f 2 (1) configurations. For the site occupancy at the higher temperature (0–1500 K, except 0 K), we computed the formation probability of twenty inequivalent configurations using the Maxwell–Boltzmann statistical distribution. Correspondingly, the Cu 2+ ions prefer to enter the 4 f 2 and 2 b sites, especially close to lanthanum layer. In order to confirm the computational conclusions, La–Cu substituted barium hexaferrites with the chemical formula of Ba 1− x La x Fe 12− x Cu x O 19 ( x = 0.0, 0.1, 0.3, and 0.5), prepared by a conventional ceramic method, were investigated by the Raman spectra and Rietveld refinement of X-ray diffraction patterns (XRD). The experiments revealed that the Cu 2+ ions are partitioned at the 2 b and 4 f 2 sites in the ratio of around 1:2. [ABSTRACT FROM AUTHOR]

The polycrystalline Ni 0.56 Cu 0.10 Zn 0.34 Fe 2− x O 4−3/2 x ( x =0.00~0.14) ferrites have been prepared by conventional oxide ceramics process. The effects of Fe-deficiency content on magnetic properties and Brillouin function characteristics for NiCuZn ferrites have been investigated in details. With the increase of Fe-deficiency content, the opposite variation trend are observed for the saturation magntic induction B s and the coercivity H c . More importantly, based on the Néel molecular field theory, for the spinel ferrites which do not only contain Fe 3+ but also some other multiple magnetic ions (Ni 2+ and Cu 2+ ), the molecular field coefficients ω aa , ω bb and ω ab= ω ba are calculated by non-linear fitting method, and the Curie temperature T c formula has been modified. With the increase of Fe-deficiency content, the values of ω aa and ω bb increase gradually, however, the value of ω ab = ω ba has a contrary trend which results in the decrease of the Curie temperature. In addition, the fitting Curie temperatures values are coincided well with the Curie temperatures calculated by the modified formula. [ABSTRACT FROM AUTHOR]

Highlights: [•] The first order crystalline constants were calculated for LiZnMn ferrite. [•] The FMR linewidth had been separated based on spin-wave approach at X-band. [•] The mechanism of dielectric polarization and dielectric loss were studied at X-band. [Copyright &y& Elsevier]

Abstract: In this paper, the effects of Sn-substitution on temperature dependence and magnetic disaccommodation of manganese–zinc ferrites were investigated. Toroidal cores were prepared by the conventional ceramic process and sintered at 1360°C for 4h in atmosphere controlled by using the equation for equilibrium oxygen partial pressure. The experimental results show that the substitution of Sn4+ in manganese–zinc ferrites can influence the thermal stability and disaccommodation remarkably. Secondly, the temperature dependence of the initial permeability μ i and disaccommodation of Sn-substitution manganese–zinc ferrites have an internal relationship. The experimental results are explained and compared with those of Ti-substitution manganese–zinc ferrite. [Copyright &y& Elsevier]

Abstract: MnZn ferrites with the chemical formula Mn0.700−x Zn0.233Co x Fe2.067O4 have been prepared by conventional ceramic technique. Toroidal cores were sintered at 1350°C for 4h in N2/O2 atmosphere with 4% oxygen. Then the influence of Co-substitution on the temperature dependence of electromagnetic properties in MnZn ferrites were investigated by measuring the magnetic properties and DC resistivity over a wide temperature ranging from 25 to 120°C. The results show that Co-substitution in MnZn ferrites results in the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to lower temperature. The Curie temperature, resonance frequency, DC resistivity and the activation energy of electron hopping increase with the increase of Co-substitution. Moreover, the drift mobility decreases with the increase of Co-substitution. However, there is little influence of Co-substitution on the microstructure with the increase of Co-substitution. [Copyright &y& Elsevier]

Abstract: MnZn ferrites with the chemical formula Mn0.68Zn0.25Fe2.07O4 have been prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350°C for 4h in N2/O2 atmosphere with 4% oxygen. Then the influence of Ta2O5 addition on the microstructure and temperature dependence of magnetic properties of MnZn ferrites was investigated by characterizing the fracture surface micrograph and measuring the magnetic properties over a temperature ranging from 25 to 120°C. The results show that, when the Ta2O5 concentration is not more than 0.04wt%, the grain size has a slight increase with the increase of Ta2O5 concentration, the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to lower temperature. However, excessive Ta2O5 concentration (>0.04wt%) results in the exaggerated grain growth and porosity increase, which make the initial permeability and saturation magnetic flux density decrease and the power loss increase at room temperature. Furthermore, the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to about 100°C. [Copyright &y& Elsevier]

Soft magnetic composites (SMCs) are widely applied in electronic devices and components, such as inductors, as they possess the highly-saturated magnetization M s of metallic materials and the highly-insulating characteristics of non-metals. However, with the development of electronic systems that require high-frequency operation, high-energy-transfer efficiency, and miniaturization, the suppression of core losses P cv in their SMCs remains a considerable challenge. Herein, we explore ways to improve the frequency dependence of core losses by using various concentrations of NiZn ferrite (0.0–5.0 wt%) to coat FeSiCr magnetic powders. The microstructural, magnetic, dielectric, and core loss performances of FeSiCr@NiZn SMCs are investigated in detail. Energy dispersive X-Ray spectroscopy (EDS) mapping confirmed that the FeSiCr magnetic powders were able to be well coated with NiZn ferrite. Core loss separation method was utilized to calculate hysteresis losses P h and eddy current losses P e from 25 to 800 kHz at 10 mT and 25 °C. With increasing NiZn ferrite concentration, both P cv and P h initially decreased and subsequently increased, while P e decreased monotonically. The sample with 3.0 wt% NiZn ferrite had the best overall performance: saturation magnetization M s = 157 emu/g, coercive force H c = 4.6 Oe, effective permeability μ e = 60, resistivity ρ = 1.25 × 104 Ω∙m, and core losses P cv = 38 mW/cm3 (at 800 kHz, 10 mT, and 25 °C). The excellent electromagnetic properties of these novel FeSiCr@NiZn SMCs give them enormous application potential in the fields of power transmission and conversion. • EDS mapping confirmed that the FeSiCr powders were well coated with NiZn ferrite. • The high-resistance layer of NiZn ferrite are beneficial for the reduction of P cv. • FSC0NZ possessed optimum P cv = 38 mW/cm3 (at 800 kHz, 10 mT, and 25 °C). [ABSTRACT FROM AUTHOR]