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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]

In certain applications, such as on-chip integrated inductors, ferrite materials are highly desirable owing to their superior magnetic and insulation properties. Spin-spray deposition is a promising method for producing high-quality thin films of ferrite, as it does not require a vacuum and can operate at low temperatures. A comprehensive analysis was conducted to investigate the influence of the substrate on the microstructure and magnetic properties of the thin films, and the growth mechanism of this phenomenon was discussed. In addition, first-order reversal curve measurements were used to study the coercivity and grain size distribution. The results indicate that thermal conductivity played a significant role in determining the thin-film growth during spin spray deposition. Polyimide is considered a more suitable substrate under this process due to its appropriate thermal conductivity, which results in more uniform grain distribution and improved magnetic properties, with maximum permeability and a cutoff frequency reaching 55 and 485 MHz, respectively. Our results provide valuable insights into the mechanism of spin-spray deposition and offer an effective way to tune the performance of ferrite thin-film materials. [ABSTRACT FROM AUTHOR]

A simple and convenient method is demonstrated in this work by continuously applying uniaxial tensile strains to tune the high-frequency properties of flexible magnetic films. The magnetostriction effect causes the uniaxial magnetic anisotropy in the Ti/Fe/Ni81Fe19/Fe/Ti multilayer film when the flexible substrate transitions from the convex state to the planar state after preparation. In addition, the microstructure, magnetic domain morphology, and the high-frequency magnetic performance of the pre-strained Ti/Fe/Ni81Fe19/Fe/Ti multilayer films are investigated. The results show that the flexible Ti/Fe/Ni81Fe19/Fe/Ti multilayer films' initial permeability can be monotonically varied over a hundred units, and the resonant frequency can be adjusted around 1.5 GHz. The flexible Ti/Fe/Ni81Fe19/Fe/Ti films, with their elastic-tunable magnetic performance, are promising candidate materials for flexible microwave devices. [ABSTRACT FROM AUTHOR]

FM (ferromagnetic)/AF (antiferromagnetic) heterogeneous multilayer films, with high-saturation magnetization (4πMs), low coercivity (Hc), and low ferromagnetic resonance (FMR) linewidth (∆H), have great application prospects in microwave/millimeter-wave devices. In this study, the Ni81Fe19 (t nm)/Fe50Mn50 (15 nm)/Ni81Fe19 (t nm) films were fabricated by DC magnetron sputtering, and the effects of thickness of the Ni81Fe19 on the microstructure, static magnetic properties and microwave properties were investigated. With the increasing thickness of Ni81Fe19 film, the saturation magnetization increased from 658 to 754 emu/m3. The in-plane and out-of-plane coercivity both decreased first and then increased, and ∆H decreased first and then raised from 193 to 95 Oe. When the thickness of the Ni–Fe film is 50 nm, the transition of the out-of-plane exchange bias field from the negative exchange bias to the positive exchange bias occurred. Remarkably, with a 50 nm Ni81Fe19 film, the multilayer films achieved excellent performance with high-saturation magnetization (4πMs, 722 emu/m3), low in-plane coercivity (Hc, 0.61 Oe), and low FMR linewidth (∆H, 95 Oe). The outstanding heterogeneous multilayer films exhibit great potentials in microwave/millimeter-wave devices. [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]

Ni 0.56+ x /2 Zn 0.34 Cu 0.1 Fe 2.0- x O 4- x ( x = 0, 0.02, 0.04, 0.06, 0.08, 0.12) ferrites have been prepared by the solid-state reaction method. The Rietveld refinement of X-ray diffraction patterns, microstructure, static magnetic properties and ferromagnetic resonance (FMR) linewidth of NiCuZn ferrites have been analyzed by X-ray diffraction, scanning electron microscopy (SEM), B-H analyzer and electron spin resonance (ESR) spectrometer, respectively. The FMR linewidth was investigated by an approximate calculation based on spin wave approach. The results revealed that all the samples were a single NiCuZn spinel phase. With the increase of iron-deficient amount, the lattice parameter ( a ) displayed a decreasing trend. However, the bulk density first increased rapidly and then trended to go up slightly. The saturation magnetization of stoichiometric NiCuZn ferrites was much lower than that of iron-deficient samples. This phenomenon is ascribed to the combined effect between molecule magnetic moment and bulk density. The magnetocrystalline anisotropy constant, derived from the law of approach to saturation, has been discussed. The anisotropy and porosity linewidth broadening models were adopted to identify the linewidth contribution. The results manifested that the porosity linewidth broadening was much larger than the anisotropy linewidth broadening. [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]

M-type barium hexaferrite (BaM) thin films with different structures ( d s100 : single-layer 100 nm thick film; d s200 : single-layer 200 nm thick film; d b200 : bilayer 200 nm thick film, where the thickness of each layer is 100 nm and the total film thickness is 200 nm) were deposited on (001) sapphire (Al 2 O 3 ) substrate by radio frequency (RF) magnetron sputtering. Effects of different structures on the crystallographic, morphological, magnetic properties and stress were investigated in details. For the structure of d s100 , BaM film processes platelet-like grains, which shows excellent magnetocrystalline anisotropy and large squareness ratio S ⊥ (0.62). For the structure of d s200 , there are a lot of acicular grains. Thus, the c-axis in-plane oriented and/or randomly oriented grains induce poor magnetocrystalline anisotropy. For the structure of d b200 , the platelet-like grains dominate the microstructure. Both squareness ratio S ⊥ (0.67) and coercivity H c⊥ (98.6 kA/m) of the d b200 show the highest values among the three kinds of the film structures. In addition, with the increase of film thickness from 100 nm to 200 nm, the stress in film decreases gradually. Compared with the other structures, the bilayer 200 nm thick film ( d b200 ) obtains the smallest stress. [ABSTRACT FROM AUTHOR]

Manganese–zinc ferrites with the composition of Mn 0.782− x Zn 0.128 M x 4+ Fe 2+ 0.09+2 x Fe 3+ 2−2 x O 4 ( x = 0; M = Ti, x = 0.004; M = Sn, x = 0.004) have been prepared by a solid-state reaction method. The cation distribution has been investigated by the Rietveld refinement of X-ray diffraction (XRD) patterns, fracture microstructure by scanning electron microscope (SEM), and magnetic property by LCR and B–H analyzer, respectively. The results show that Ti 4+ and Sn 4+ ions prefer to occupy octahedron sublattices (B sites), which leads to an increase in lattice parameter. Sn 4+ ions substituted MnZn ferrite has much denser and more uniform microstructure with smaller grains than that of Ti 4+ ions substituted and unsubstituted MnZn ferrites. The Curie temperature ( T c ) of Ti 4+ and Sn 4+ substituted MnZn ferrites is higher than that of unsubstituted sample. In addition, both Ti 4+ and Sn 4+ substitutions, due to the compensation of magnetocrystalline anisotropy constant, can move the secondary peak of μ i ∼ T curve to low temperature. However, the opposite variation trend has been observed in a P L ∼ T curve. Also, the DC-bias superposition characteristics 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]

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: 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]

This work demonstrates the dependence between magnetic properties and the thickness of NiFe thin films. More importantly, a quantitative study of the surface composition of NiFe thin film exposed to atmospheric conditions has been carried out employing angle-resolved X-ray photoelectron spectroscopy (ARXPS). In this study, we fabricated Ni81Fe19 (NiFe) thin films on Si (100) substrate using electron beam evaporation and investigated their surface morphologies, magnetic properties, and the thickness of the surface oxide layer. The coexistence of metallic and oxidized species on the surface are suggested by the depth profile of ARXPS spectra. The thickness of the oxidized species, including NiO, Ni(OH)2, Fe2O3, and Fe3O4, are also estimated based on the ARXPS results. This work provides an effective approach to clarify the surface composition, as well as the thickness of the oxide layer of the thin films. [ABSTRACT FROM AUTHOR]

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]

Abstract: MnZn ferrites were prepared by conventional oxide ceramic process. The effects of Bi2O3 on microstructure and magnetic properties of MnZn ferrites were investigated by means of characterizing the fracture surface micrograph, composition of grain boundary, magnetic properties and density by scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDS), B-H analyzer and Archimedes method, respectively. The results indicate that Bi2O3 mainly segregates and concentrates in the grain boundary regions, promotes solid-state reaction and grain growth, reduces porosity and enhances density. Optimum addition of Bi2O3 increases the permeability and saturation magnetic induction, meanwhile ensures the well frequency stability of permeability. [Copyright &y& Elsevier]

Gas atomization and multi-layer coating are widely used powder fabrication techniques to prepare soft magnetic composites (SMCs) utilized in high-power low-loss power electronics. However, the diverse morphologies of gas-atomized powders significantly impact coating effectiveness, subsequently influencing the soft magnetic properties of SMCs. Herein, FeSiAl-based SMCs with different particle shapes and a multi-layer coating of phosphate and heat-resistant silicone resin are prepared to explore the synergetic effects of particle shape and coating on magnetic performances. Compared with dumbbell-shaped powder, the spherical powder has a regular shape and strong flowability, resulting in a close-packing structure of the magnetic core. The spherical particle with a large specific surface area promotes efficient insulation coating effects. The dumbbell-shaped particles are potentially prone to cause pores and defects during the high-pressure compaction process, leading to poor dense packing and magnetic loss performance. With a similar average particle size, the magnetic core prepared by spherical powders exhibits a larger interface area, resulting in a greater demagnetizing field after phosphating passivation, thus significantly improving the DC-bias performance. The FeSiAl-based magnetic core prepared by spherical powders with 1.5 wt% phosphoric acid passivation has better magnetic loss and DC-bias properties than that by dumbbell-shaped powders, showing a stable permeability of 60.4, core loss of 286.2 mW/cm3 at 100 mT, 100 kHz, and DC bias characteristic of 49.1 % at a DC superposition field of 100 Oe. • We explore the synergetic effects of particle shape and insulation coating on magnetic performances. • The spherical particle contributes to a dense packing structure and a greater interface area of the magnetic core. • The spherical powders and multi-layer coatings are conducive to significantly improving DC-bias properties. • The FeSiAl cores with low loss and high DC-bias properties are fabricated by tailoring the particle shape coatings. [ABSTRACT FROM AUTHOR]

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]

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]

M-type strontium (SrM) hexaferrites exhibiting large magnetocrystalline anisotropy, high saturation magnetization and coercivity, and narrow ferrimagnetic resonance (FMR) linewidth have a great potential for applications in high-performance motors and self-biased circulators. Ca doping in SrM hexaferrites is an effective method for tailoring the intrinsic electromagnetic parameters and modifying polycrystalline microstructure to meet the application requirements. However, the regulation mechanism of Ca doping is still obscure, and its regulation effect is not optimized. Here, the magnetic and electrical properties of SrM hexaferrites with site-controlled two-step Ca doping are reported. The spatial concentration distribution and diffusion dynamics of Ca2+ ions are investigated when introduced by CaCO 3 as the reactant and sintering additive, respectively. The existence of the Ca2+ ions in the crystallites added as the reactant reduces the diffusion of the Ca2+ ions in the grain boundaries added as the additive, which synergistically tailors the magnetocrystalline anisotropy field, crystallite orientation, and polycrystalline morphology, and further optimizes the coercivity, remanence, and maximum energy product. Moreover, the impact of the Ca2+ ions on the resistivities of the grain and grain boundary is also investigated, revealing the synergetic effect of Ca2+ ions at different sites on lowering the loss. These results prove the effectiveness of the site-controlled two-step Ca doping in synergistically enhancing the magnetic and electrical properties of SrM hexaferrites. [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]

Two series of W- and M-type composite hexaferrites were synthetized using the conventional ceramic method in two different synthesis routes. In the first synthesis route, W- and M-type composite hexaferrites were formed by reaction in the pre-sintering stage. In the second synthesis route, W- and M-type composite hexaferrites were obtained by physically mixing W- and M-type hexaferrites in the second ball milling stage. The influence of M-type phase on the structure and magnetic properties of W-type hexaferrites synthesized in both synthesis routes are investigated in detail. For both synthesis routes, X-ray diffraction (XRD) patterns of all samples indicated crystallization of W- and M-type hexaferrites phase and scanning electron microscopy (SEM) measurements revealed hexagonal platelet-like grains. In the pre-sintering stage, the saturation magnetization (4π M s) of all samples ranged between 3.30 kG and 4.25 kG. The remanence ratio (M r / M s) changed from 0.77 to 0.88 with the increase of pre-sintering temperature. The coercivity (H c) of all samples ranged between 456 Oe and 1846 Oe. The ferromagnetic resonance (FMR) linewidth (Δ H) ranged between 466 Oe and 748 Oe. In the second ball milling stage, 4π M s and M r / M s maintained a relatively stable value of ~4.5 kG and ~0.89, respectively. H c increased from 519 Oe to 620 Oe with the increase of M-type hexaferrites. Δ H ranged between 317 Oe and 573 Oe. We note that in both synthesis routes only the composite hexaferrites synthesized in the pre-sintering stage have a significantly improved coercivity from 456 Oe to 1846 Oe. This enhancement in coercivity is attributed mainly to the effect of exchange coupling among ferrite grains. In addition, the Δ H decreases with the addition of M-type hexaferrites. [ABSTRACT FROM AUTHOR]

Strontium ferrites, which exhibit large remanence, high coercivity (H c), are fascinating for applications in motors and high-frequency microwave devices. Here we demonstrate the strontium ferrites (Sr 0.34 Ca 0.25 La 0.41 Fe 11.4 Co 0.19 O 19-δ) sintered at 1150 °C with enhanced magnetic properties through constructing magnetoelastic stress. The effects of applied pressure (P c -axis) of 0–16 kPa during the sintering process on phase compositions, morphologies, magnetic and microwave properties are investigated in detail. We note that the P c -axis could contribute to enhanced c -axis preferred orientation. This mechanism of enhancement has been also discussed according to the magnetoelastic theory. By applying an external pressure of 8 kPa, intrinsic coercivity (H cj) of 4657 Oe and magnetic coercivity (H cb) of 3781 Oe are obtained. The increments are 8.1% and 18.0% for H cj and H cb , respectively, compared to the sample with P c -axis of 0 kPa. However, the enhancement of H c by the P c -axis is seen to be limited above 8 kPa, which can be attributed to the enlarged grain size and porosity observed. In addition, the ferromagnetic resonance frequency (f r) is also increased by the increased P c -axis. [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]

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]

• CCTO can improve the uniformity of grains and lowered the porosity. • CCTO dopant can obviously improve the electromagnetic properties of MnZn ferrites. • The suppression of core losses P L at 3 MHz 30 mT is affected by hysteresis loss P h and eddy current loss P e. • This work reveals that doping dielectric materials to suppress core losses of MnZn ferrites is feasible. To obtain miniaturized, lightweight, and integrated power conversion devices, the core material must be suitable for operation at higher frequencies (in the megahertz range) and must exhibit excellent performance, specifically, low core losses. In this study, MnZn power ferrites, a common core material, were doped with calcium copper titanate (CCTO) using a solid-state reaction method. The effects of CCTO doping (0.0–0.5 wt%) on the structural, magnetic, and dielectric properties of the MnZn ferrites were studied. The addition of 0.2 wt% CCTO to the MnZn ferrites improved the grain uniformity and decreased the porosity; thus, the material exhibited a fine microstructure. In addition, the saturation induction, initial permeability, and resistivity of the MnZn ferrites were increased, and the high-frequency core losses were suppressed. The core losses of the 0.2 wt% CCTO sample were only 495 kW/m3 at 3 MHz, 30 mT, and 25 °C. The lower core losses resulted mainly from reductions in the hysteresis loss and eddy current loss. The real permittivity of two representative MnZn ferrite samples was also investigated. The application of state-of-the-art MnZn ferrites with superior electromagnetic properties in high-frequency power conversion devices is anticipated. This study demonstrates that adding a dielectric material improves the electromagnetic properties of MnZn power ferrites. [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]

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]

M-type hexaferrites which exhibit strong uniaxial anisotropy field, are promising for the applications in self-biased microwave and millimeter wave (MMW) devices. Here we demonstrate crystallographically textured hexaferrites with narrow ferromagnetic resonance (FMR) linewidth synthesized by the conventional ceramic method. Meanwhile, the relationship between iron-deficiency content and microstructure, crystallographic, and magnetic properties are researched. These hexaferrites have strong remanence ratio of above 0.9 along c -axis. By fitting of Lorentzian function to absorption derivative, we probe detailedly into the zero-field FMR linewidth of Ba 0.8 La 0.2 Fe 11.8- x Cu 0.2 O 19-δ hexaferrites. When x equals 1.0, it indicates the narrowest FMR linewidth of 324Oe, as compared with previous reports for crystallographically textured hexaferrites. [ABSTRACT FROM AUTHOR]

With the urgent need for high-power low-loss microwave systems, next-generation wireless communications call for high-performance yttrium iron garnet with narrow ferrimagnetic resonance (FMR) linewidth, large spin-wave linewidth, and high Curie temperature, which can be tailored by cation substitution and vacancy engineering. Here, the electromagnetic properties of vacancy-engineered Gd3+-substituted garnet ferrites are reported. Cation vacancies on the dodecahedral sites of the garnet crystal structure are introduced by deficient Gd3+ substitution for the Y3+ ions. The polycrystalline microstructure, magnetic properties, and electrical properties of both the Gd3+-sufficient and Gd3+-deficient samples are comprehensively examined and compared. The deficient Gd3+ substitution promotes the densification process and grain growth during the sintering stage. Without detriment to the spin-wave linewidth and electrical resistivity, the vacancies are beneficial to reducing the FMR linewidth and increasing the Curie temperature. With appropriate vacancy concentrations, the garnet ferrite samples exhibit a 58% reduction in the FMR linewidth and a 13% increase in the Curie temperature. These results reveal the great potential of the vacancy-engineered Gd3+-substituted garnet ferrites for high-power low-loss microwave communication systems. • Cation vacancies on the 24 c sites are created by deficient Gd3+ substitution. • Cation vacancies promote densification and grain growth during sintering. • Cation vacancies narrow the FMR linewidth and increase the Curie temperature. • Cation vacancies have no detriment to the spin wave linewidth and resistivity. [ABSTRACT FROM AUTHOR]

The metallic magnetic thin films are widely used in high-frequency magnetic devices, the reliability of which greatly depends on the saturation magnetization (M s) and resonance frequency (f r) of the films. However, increasing the operating frequency of the magnetic thin film is extremely challenging. This study investigates the microstructure, magnetic domains and magnetic properties of obliquely deposited Ti/Fe/Ni 81 Fe 19 /Fe/Ti multilayer films. The coercivity distribution of the deposited films is investigated by first order reversal curve (FORC) measurements. The result of static magnetic properties revealed the in-plane uniaxial anisotropy with a high anisotropy field (H k) up to 495 Oe. A magneto-optical Kerr microscope image displayed the multi-step magnetization reversal processes at different oblique angles. Complex permeability spectra indicated that the resonance frequency increases from 1.27 to 4.71 GHz as the deposition angle is increased from 0° to 25°. Thus, Ti/Fe/Ni 81 Fe 19 /Fe/Ti multilayer film with tunable magnetic performances is one of the good candidate materials for microwave devices. • This study investigates the microstructure, magnetic domains and magnetic properties of Ti/Fe/Ni 81 Fe 19 /Fe/Ti films. • The self-shadowing effect is observed in the films deposited at 15°, which showed an obvious columnar structure. • The dynamic magnetic properties show that the oblique deposition angle can tune the f r of samples from 1.27 to 4.71 GHz. [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]

Abstract: Barium hexaferrite thin films were deposited on Si (100) substrates using a radio frequency magnetron sputtering system. The effects of oxygen partial pressure during deposition process on the material characteristics and magnetic properties of BaM thin films were investigated. X-ray diffraction data indicated that with the oxygen partial pressure ratio increasing from 0% to 8%, the diffraction peaks shift slightly towards the larger angles and the corresponding lattice parameters (a and c) decrease. The saturation magnetization (M s) ranges from 200 to 358kA/m as the oxygen partial pressure ratio is varied from 0% to 8%. These changes are attributed to the different oxidation states of Fe ions in the films with oxygen excess or vacancies. When deposited with 1% oxygen partial pressure, the film possesses the highest saturation magnetization (358kA/m) and exhibits better perpendicular c-axis orientation in comparison with those deposited without oxygen partial pressure or with higher oxygen partial pressure. [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 Mn0.68Zn0.25Fe2.07O4 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]

• Magnetic properties of SrM hexaferrites are regulated by changing Bi 2 O 3 additive. • All samples showed strong uniaxial anisotropy as Bi 2 O 3 additive amount increased. • When Bi 2 O 3 additive x = 1.0 wt%, the overall performance of sample is the best. • Theory of independent grain approximation was adopted to divide the FMR linewidth. Considering the improvement of electronics regarding high frequency and miniaturization, SrM hexaferrites need to exhibit high anisotropy field H a , high remanence ratio M r / M s , and low ferromagnetic resonance linewidth Δ H to create microwave devices and equipment with planarisation, miniaturisation, and high frequencies. The key to achieving self-biased microwave devices with high-frequency is to simultaneously achieve high H a , high M r / M s , and low Δ H. However, it is hard to meet these requirements. In this study, Sr 0.4 La 0.3 Ca 0.3 Fe 11.85 Al 1.0 Co 0.15 O 19 was used to study the effect of different doping amounts of Bi 2 O 3 on its magnetic characteristics, micromorphology and FMR linewidth. With the increase of Bi 2 O 3 doping, the grain size of the sample gradually increased, and the uniformity of the grain size gradually decreased. When the Bi 2 O 3 doping amount x increased from 0 to 1.2 wt%, the 4π M s and 4π M r values increased and the coercivity displayed the opposite tendency. The samples showed great uniaxial anisotropy. The magnetocrystalline anisotropy field H a shows a trend of initially decreased and then increased. When x = 1.0 wt%, H a reaches the maximum value of 28.9 kOe. At this time, the ferromagnetic resonance linewidth Δ H of the sample is 1578 Oe. The theory of IGA was adopted to divide the FMR linewidth into two parts Δ H a and Δ H p. Accroding to the results, Δ H a takes the bigger proportion of linewidth. However, the change in Δ H p is not negligible. When x = 1.0 wt%, the sample showed its best performance (4π M s = 3412 Gs, 4π M r = 2905 Gs, H c = 2649 Oe, M r / M s = 85.1%, large H a = 28.864 kOe, and Δ H = 1578 Oe). The SrM ferrite materials provided in this study can potentially be used in the microwave engineering, high-frequency, and self-biased devices. [ABSTRACT FROM AUTHOR]

Abstract: The effects of sintering temperature and Bi2O3 content on the microstructure and magnetic properties of lithium–zinc (LiZn) ferrites prepared by a conventional ceramic method were investigated. The results show that the densification behavior and grain growth rate were greatly improved by the addition of Bi2O3, because a liquid phase sintering occurred during the sintering process at high temperature due to the low-melting point of Bi2O3 (825°C). X-ray diffraction (XRD) patterns of the slightly doped samples did not reveal the appearance of any phase other than spinel LiZn ferrite. However, the secondary phase of perovskite BiFeO3 was detected for Bi2O3 content of more than 0.25wt%. The studies further show that Bi oxide was present at grain boundary, and promoted the grain growth as reaction center at lower temperature. A high saturation magnetization, squareness ratio, minimum ferromagnetic resonance linewidth and low coercive force were obtained for the sample with 1.00wt% Bi2O additive at lower sintering temperature (1100°C). [Copyright &y& Elsevier]

• Static magnetic and microwave properties of Fe/NiFe/Fe films are regulated by Fe thickness. • The strong pinning effect has been found when the thickness of Fe reaches 4 nm. • The value of the exchange stiffness is obtained by fitting the PSSW mode. Microwave devices, designed by the electromagnetic characteristics of spin waves, are widely used in radio frequency circuits and microwave systems, such as magnetic tunable filters, frequency multiplier, and signal-to-noise ratio enhancers. In order to manufacture these devices, it is not only the saturation magnetization (4π M s) and ferromagnetic resonance linewidth (Δ H) that need to be regulated, but also the exchange stiffness (A). In this study, the Fe (t nm)/Ni 81 Fe 19 (50 nm)/Fe (t nm) multilayer films were proposed to regulate the 4π M s , Δ H , and A , which were fabricated using electron beam evaporation, and the dynamic magnetic properties of the film were studied by ferromagnetic resonance (FMR) spectroscopy. Firstly, we obtain the 4π M s , γ and H a by fitting the uniform FMR mode. Then we obtain the exchange stiffness by fitting the first (p = 1) perpendicular standing spin wave (PSSW) mode. With the increasing Fe film thickness, the calculated saturation magnetization increased from 9250 to 14060Gs, FMR linewidth increased from 111.5 to 140.3Oe and the exchange stiffness decreased from 22.1 × 10−12 to 7.8 × 10−12J/m. [ABSTRACT FROM AUTHOR]

• Static magnetic and microwave properties of Fe/NiFe/Fe films are regulated by Fe thickness. • The strong pinning effect has been found via the PSSW mode when the thickness of Fe reaches 4 nm. • With 8 nm Fe film, the film achieved optimum performance with high 4π M s , low H r , and low ∆ H. Multilayer films with high saturation magnetization and low ferromagnetic resonance linewidth have great potential for various applications in the era of high frequency and miniaturization. In this study, Fe (t nm)/Ni 81 Fe 19 (50 nm)/Fe (t nm) multilayer films were fabricated using electron beam evaporation, and the microstructure, saturation magnetization, coercivity, ferromagnetic resonance (FMR) linewidth and perpendicular standing spin-wave (PSSW) mode are discussed in detail. With increasing Fe film thickness, the saturation magnetization of the multilayer films increased from 10,547 to 14,494 Gs, becoming closer to the theoretical value, and the ferromagnetic resonance linewidth showed an overall increasing trend. It is worth noting that a strong pinning effect has been found via the appearance of the PSSW mode in the FMR spectrum, when the thickness of Fe reaches 4 nm. As the thickness of the Fe film increased from 4 to 15 nm, the perpendicular standing spin-wave field (H p) increased from 133 to 379 Oe, and the perpendicular standing spin-wave linewidth (Δ H p) increased from 68 to 148 Oe. Remarkably, with 8 nm thick Fe film, the multilayer films achieved excellent comprehensive performances with high saturation magnetization (4π M s , 13,525 Gs), a low in-plane ferromagnetic resonance field (H r , 725 Oe), and a low FMR linewidth (Δ H , 84.24 Oe). [ABSTRACT FROM AUTHOR]