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In the present work, the Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite, a low temperature sintered gyromagnetic material, was prepared via solid-state reaction method. A pure spinel phase can be formed with a sintering temperature ranging from 880°C to 920°C, which allows them to be co-fired with silver. The addition of ZnO-Bi2O3-SiO2 ( ZBS) glass in the Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites contributes significantly to the grain growth and ferromagnetic properties through a low temperature (~900°C) sintering process. Results show that the addition of ZBS glass (0.125-2.00 wt%) cannot only double saturation induction (from ~150 to 300 mT) but also drastically reduce ferromagnetic resonance line width at 9.3 GHz (from 920 to 228 Oe), indicating that ZBS glass is a good candidate for lowing the sintering temperature of LiZnTi ferrites. [ABSTRACT FROM AUTHOR]

The influences of \ Nb2{\ {O}}5 addition on the microstructure and magnetic properties, especially DC-bias-superposition characteristic of the low-temperature-fired NiCuZn ferrites, were investigated. It was found that Nb ions entered into the lattice when \ Nb2{\ {O}}5 content was less than 0.3 wt%, after that, a second phase, bismuth iron (zinc or nickel) niobium oxide appeared. The second phase consumed some sintering aid \ Bi2{\ {O}}3 and had obvious influences on sintered density, grain size and magnetic properties, such as permeability of the ferrites. All of the sintered density, saturation magnetic flux density and average grain size gradually decreased with \ Nb2{\ {O}}5 content. Initial permeability first increased, and then continuously decreased with \ Nb2{\ {O}}5 content. The sample with 0.1 wt% \ Nb2{\ {O}}5 displayed the highest initial permeability, which was mainly due to the decrease of magnetocrystalline anisotropy constant. Under relatively low superposition magnetic field (\ H\leq 375\ \ A/m), a higher initial permeability favored to obtain a higher incremental permeability. However, when the superposition magnetic field continued to increase, some samples with a lower initial permeability displayed a higher incremental permeability. The normalized incremental permeability was mainly determined by the coercivity of the samples. A higher coercivity favored the attainment of a better DC-bias-superposition characteristic on normalized permeability. So the sample with 0.5 wt% \ Nb2{\ {O}}5, which displayed the largest coercivity, had the best performance. Possible mechanisms contributing to the above results were discussed in detail. [ABSTRACT FROM AUTHOR]

The influence of microstructure on the magnetic properties, especially the dc-bias-superposition characteristics, of NiZn ferrites has been investigated. The value of saturation magnetic flux density (Bs) first increased and then changed little with variation of the sintered density, and showed little relation to the microstructure. Coercivity (Hc) decreased continuously with increasing average grain size. \DeltaB (Bs-remanence) first increased with increasing average grain size, but then gradually decreased when abnormal grain growth prevailed. The incremental permeability (permeability with magnetic field superposition) was influenced by both \DeltaB and Hc. A sample with higher \DeltaB and Hc favored the attainment of a higher incremental permeability. The Q-factor was mainly determined by the sintered density and microstructure. To sum up, a uniform and dense microstructure with relatively small average grain size is favorable for obtaining better dc-bias-superposition characteristics, including permeability and Q-factor. [ABSTRACT FROM AUTHOR]

Traditional low-temperature-fired NiCuZn ferrites (900^\circC sintered) were generally prepared at relatively low calcination temperatures to increase the activity of the calcined powders and promote sintering. However, in this study, we changed the calcination temperature from 700^\circC to 1000^\circC to investigate the influences of high calcination temperature on the densification characteristic and magnetic properties of the low-temperature-fired NiCuZn ferrites. It was found that although a high calcination temperature decreased the activity of the calcined powder, the NiCuZn ferrite could attain a higher sintered density with an adequate sintering aid. Furthermore, a uniform microstructure with small average grain size was obtained for the sample calcined at 1000^\circC with 1 wt% Bi2O3 sintering aid. It also displayed high performances on Q-factor and permeability. Hence, choosing a high calcination temperature and adding more sintering aid was also an option for obtaining high performance and low-temperature-fired NiCuZn ferrites. [ABSTRACT FROM AUTHOR]

A series of soft magnetic nanogranular CoFe-TiO2 films with different thicknesses were fabricated on Si substrates by co-sputtering CoFe and TiO2, and the magnetic and high frequency properties were studied in details. X-ray diffraction analysis confirmed that the films were nanocrystalline/amorphous composites. A saturation magnetization as high as 21 kGs and a ferromagnetic resonance (FMR) frequency above 3 GHz were obtained. It was found that the coercivity decreased steeply with the increase of film thickness and its minimum value was about 6 Oe. In addition, the variations of FMR peak broadness of the imaginary part and damping factor were also presented and discussed as functions of film thickness. [ABSTRACT FROM AUTHOR]

We demonstrate that the spin pumping effect can be effectively tuned with nitriding the nonmagnetic layer in ferromagnetic/nonmagnetic (FM/NM) bilayer system. Series of Ni81Fe19/CuNx bilayer films were prepared by magnetron sputtering with different nitrogen partial pressures from 0% to 20%. The static magnetic properties of the Ni81Fe19/CuNx bilayer films were studied by vibrating sample magnetometer and dynamic magnetic properties was studied using a coplanar waveguide vector-network-analyzer ferromagnetic resonance spectrometer with an in-plane configuration. The results reveal that the static magnetic properties are not noticeably changed with capping a nitrified copper layer. Both the linewidth and the Gilbert damping parameter are strongly influenced by the nitrogen partial pressure during the copper layer nitride process. The spin-mixing conductance of the NiFe/CuNx bilayer films was quantified from the peak-to-peak linewidth of ferromagnetic resonance spectra based on the model of the spin pumping. [ABSTRACT FROM AUTHOR]

Undoped Bi2FeCrO6 and 10 at. % La-doped Bi2FeCrO6 were prepared by a high-pressure solid-state sintering method. The phase structure, electrical, ferroelectric, and magnetic properties have been investigated. It is shown that doping La can increase the resistivity by three orders of magnitude at room temperature. Furthermore, La-doped Bi2FeCrO6 shows an enhanced magnetization, about three times that of undoped Bi2FeCrO6, and a high coercivity of ∼210 Oe. [ABSTRACT FROM AUTHOR]

A series of (Ni80Fe20)1-x(Ni0.5Zn0.5Fe2O4)x films were fabricated on Si substrates by means of radio frequency magnetron sputtering and the electrical and magnetic properties were studied. Optimal films with the desired properties of low coercivity Hc ∼ 4 Oe, high saturation magnetization 4πMs ∼ 14.5 kG, and high electrical resistivity ρ ∼ 1500 μΩ cm were obtained. The permeability spectra measured shows that its natural ferromagnetic resonant frequency was about 3.4 GHz. The tested results shown that the sputtering power had an important effect on the films properties and that it can be convenient to adjust the natural ferromagnetic resonant frequency of the films. [ABSTRACT FROM AUTHOR]

Crystal structure, microstructure, static and dynamic magnetic properties of Ba 3-x Nd x Co 2 Fe 24 O 41 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) ceramics were investigated. Samples were prepared via sintering at 1250 °C for 4 h, and XRD results revealed their crystal structure after Nd substitution. With the increase in Nd3+ ion dopant content, particle porosity increased, leading to slight decrease in volume density. Static magnetic data showed the weak effect of Nd-substitution on saturation magnetization strength and a slight increase in coercivity (from 52 Oe to 75 Oe at x = 0–0.5), while out-of-plane magnetic anisotropy rose significantly (from 10.1 kOe to 14.5 kOe at x = 0–0.5). Dynamic magnetic tests demonstrated noticeable decrease in permeability (from 17 to 8), whereas cutoff frequency increased from 0.8 GHz to 1.9 GHz and the maximum Snoek product reached 18.8 GHz for the sample with x = 0.4. The fitting of real part of permeability using domain wall resonance and natural resonance models revealed that resonance frequency and out-of-plane anisotropy both increased with Nd-substitution. Moreover, despite Nd doping, samples maintained low magnetic loss and high Q value within higher frequency range. Therefore, findings of this study provide a pathway to development of substituted Z-type barium (Co 2 Z) ferrites for high frequency applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Nb-doped Z-type hexaferrites (Ba3(Co0.4Zn0.6)2Fe24O41) with composition of Ba3(Co0.4Zn0.6)2Fe24O41+x Nb2O5 (where x=0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.2, 1.6 and 2.0wt%) were prepared by a solid-state reaction method. The effects of different sintering temperature (T s) and Nb2O5 content on the sintering behaviors, phase composing, microstructure, and magnetic properties of the samples were investigated. The results from X-ray diffraction and scanning electron microscopy show that as the amount of Nb2O5 additive increases, the major phase changes to Z-phase, Simultaneously, M-phase and a small amount of niobate phase appear. The Nb2O5 additive promotes the grain growth as reaction center at lower sintering temperature (1220°C), but at higher temperature (1260°C), niobate phase separated out in grain boundaries as secondary phase will restrain abnormal grain growth, so closed pores in grains are not formed. The Nb2O5 additive can enhance densification, improve initial permeability of hexaferrites by increasing the grain growth of hexaferrite and the displacement of ions in the sintering process due to the aberration and activation of crystal lattice, which is accompanied by the solubility of Nb5+ in the hexaferrites. A relative density of 96%, maximum initial permeability (32–33), minimum coercivity (454–455A/m) and resonance frequency above 400MHz were obtained for the sample with 0.8wt% Nb2O5 sintered at 1260°C for 6h. [Copyright &y& Elsevier]

Soft-magnetic high-entropy alloy (HEA) Fe 33 Co 28 Ni 28 Ta 5 Al 6 were prepared by laser-melting deposition (LMD). The microstructures and mechanical as well as magnetic properties of the fabricated samples were investigated. All samples comprised face- and body-centered cubic phases, where the proportion of the latter increased when the laser power was increased from 800 to 1400 W. With the increasing laser power, the yield strengths of the samples decreased slightly, and the saturation magnetization (B S) of the samples remained at approximately 1.07 T, the coercivity increased from 1034 A/m to 4456 A/m. The study showed that high laser powers resulted in high stress levels and increased the blocking effect on the motion of the magnetic domain walls of the samples. This work would provide a path way for the rapid manufacturing of high-performance soft-magnetic HEAs. • Prepared a soft-magnetic high-entropy alloy via laser-melting deposition (LMD). • Obtained a soft-magnetic material with good yield strength (1380 MPa) at a laser power of 800 W. • The mechanical and magnetic properties of the alloy can be improved via adjusted the laser powders. [ABSTRACT FROM AUTHOR]

Adjusting the phase composition of high-entropy alloys is an effective approach to change its mechanical and magnetic properties. In this study, FeCoNiCr high-entropy alloys with Al addition (Al x FeCoNiCr; x = 0.0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.75) were prepared by argon arc melting to obtain a special spinodal decomposition structure. There precipitated body-centered cubic (BCC) phase in the face-centered cubic (FCC) phase matrix for the samples with Al (x = 0.25, 0.5, 0.75) addition. Furthermore, the increase in the Al content (x = 1.0, 1.25, 1.75) transformed the alloy into a BCC phase, and resulted in a spinodal decomposition in the alloy. This spinodal decomposition created a low-misfit coherent nanostructure combining the enriching AlNiCo ordered B2 matrix with enriching Fe–Cr BCC disordered nanoprecipitates. The difference in the distribution of chemical elements of the two phases leads to different magnetic properties and induces the magnetoresistance (MR) effect. This provides a pathway for the design of advanced functional high-entropy alloys. [Display omitted] • Spinodal decomposition can induce magnetoresistance (MR) in AlFeCoNiCr alloy. • The magnetic and nonmagnetic phase is necessary condition for inducing MR effect. • The mechanical and MR properties can be controlled by spinodal decomposition. [ABSTRACT FROM AUTHOR]

In the present work, Li 0.35 Zn 0.30 Mn 0.05 Ti 0.15 Fe 2.15 O 4 ferrites were successfully synthesized via solid-state reaction method with the assistance of Bi 2 O 3 -MgO mixture. It was observed that a pure spinel phase could be formed at low temperatures (880 °C–920 °C), suggesting the compatibility of co-firing with silver internal electrodes. The employment of Bi 2 O 3 -MgO mixture could not only achieve the low-temperature sintering, but also facilitate the grain growth and subsequently promote the magnetic properties. SEM results revealed that the ferrites grain size was significantly increased (from 1 to 20 μm) with an appropriate dopant addition (1.2 wt %). Meanwhile, the saturation induction was enhanced from 141.2 to 345.9 mT, the coercivity was decreased from 515.2 to 176.6 A/m, and the FMR linewidth was dramatically decreased from 749.0 to 245.0 Oe at 9.3 GHz. Thus it is expected that the improved properties will allow the Li 0.35 Zn 0.30 Mn 0.05 Ti 0.15 Fe 2.15 O 4 ferrites to be a promising candidate for low temperature co-fired ceramics (LTCC) applications. Image 1 • Low-temperature preparation of LiZn ferrites (below 950 °C). • All the samples with Bi 2 O 3 -MgO mixture show a typical spinel structure. • Bs increased from 141 to 345 mT with the ΔH decreased from 749 to 245 Oe. [ABSTRACT FROM AUTHOR]

In this work, high quality yttrium-iron-garnet (YIG) thin films were fabricated on a Ga 3 Gd 5 O 12 substrate by pulsed laser deposition (PLD). The material composition, iron ion valences and magnetic properties of the YIG films were systematically investigated as a function of annealing temperature. X-ray diffraction and Raman spectroscopy measurements demonstrate optimal YIG film crystallinity when annealed at 800 °C. X-ray photoelectron spectroscopy confirms the Fe2+ ions were strongly suppressed in YIG thin film after annealed at 800 °C. In this case, 60 nm-thick YIG films exhibit excellent magnetic properties having bulk-like saturated magnetization (1755 Gs), a minimized ferromagnetic resonance linewidth (8.3 Oe) and a low Gilbert damping parameter of 5.76 × 10−4. Our study prove that suitable annealing conditions play a critical role on garnet composition, iron ion valences and magnetic properties for PLD grown high quality YIG thin films, which have great potential in the fabrication of low dissipative spintronic devices. • Annealing plays a critical role on microstructure and magnetic properties of YIG film. • The increase of Fe2+ iron contents lead to additional absorption peaks in the FMR spectra. • 800 °C annealed films own the optimal element ratio and the Fe3+ iron contents. • Surface roughness and crystallinity have great influence in achieving a low damping. [ABSTRACT FROM AUTHOR]

Tuning the magnetic anisotropy of nanoparticle assemblies is critical for their applications such as on-chip magnetic electronic components and electromagnetic wave absorption. In this work, we developed a facile hierarchical self-assembly method to separately control the magnetic shape and magnetocrystalline anistropy of individual nanoparticle assemblies in arrays. Since magnetic nanoparticle assemblies in the array have the same size, shape and alignment, we are able to study the magnetic properties of individual nanoparticle assembly by measuring the whole arrays. The interplay between the two magnetic anisotropies was systematically studied for disk- and bar-shaped nanoparticle assemblies. Maximum magnetic anisotropy was obtained when the easy axis of magnetic nanoparticles was aligned along the long axes of the bar-shaped nanoparticles assemblies. [ABSTRACT FROM AUTHOR]

Abstract: The composition effects on the dielectric and magnetic properties of NiCuZn–BaTiO3 composites fired at low temperature were investigated. The coexistence of perovskite BaTiO3 and spinel ferrite phases in the composites were observed; no significant chemical reactions occurred between BaTiO3 and NiCuZn ceramics during sintering. The nanosized BaTiO3 powders favored a decrease in grain size. The saturation magnetization, remanent magnetization and real permeability continuously decreased with increasing BaTiO3 content. And the real permittivity continuously increased with the BaTiO3 content. The Q-factor (quality factor) exhibited relatively high values with 20–30wt% BaTiO3. All composite materials exhibited a low dielectric loss below 100MHz. Synthetically considerations, the composites with 20–30wt% BaTiO3 could obtain relatively high real permeability and real permittivity values, and the magnetic and dielectric losses were relatively low, so they were the best candidates to produce LC-integrated chip elements. [Copyright &y& Elsevier]

Abstract: Z-type hexaferrites with composition of Ba3(Co0.4Zn0.6)2Fe24O41+x wt% Bi2O3 (where x=0–2) were prepared by a solid-state reaction method. The effects of different mixing procedures and Bi2O3 content on the sintering behavior, phase composition, microstructure and magnetic properties of the samples were investigated. It was confirmed that with the same secondary mixing time (t 2), increasing the primary mixing time (t 1) leads to a decrease of the average grain size and an increase of the initial density. The initial density and the distribution of particles and pores determined the sintering density. With t 1=24h and t 2=6h, the sintering density reached its maximum. The initial permeability and Q-factor also peaked, which could be attributed to the highest sintering density and compact microstructure. Further studies showed that with increasing Bi2O3 content, the major phase changed to the Z-phase; simultaneously, the remnants content of intermediate phase decreased. The Bi2O3 additive, as a reaction center, promoted the grain growth at lower temperatures. The decrease of the sintering temperature and the partial agglomeration of Bi2O3 on the grain boundaries restrained abnormal grain growth, thus closed pores in grains were not formed. A maximum initial permeability, a higher Q-factor, a cut-off frequency of 900MHz and a resonance frequency above 1.8GHz were obtained for the sample with 0.6wt% Bi2O3 sintered at low temperature. [Copyright &y& Elsevier]

• (TmBi) 3 (FeGa) 5 O 12 nanostructured films were sputtered on high quality liquid phase epitaxy Y 3 Fe 5 O 12 films. • Crystal structure and magnetic hysteresis loop measurement indicate interfacial tension between the YIG TBIG films. • The stress induced anisotropy up to 220.0 Oe results in multi-mode ferromagnetic resonance. • The heterostructure induction and strengthening of magnetoelastic coupling between spin and elastic subsystems. We studied the static and dynamic magnetic properties of a Y 3 Fe 5 O 12 /Tm 2.28 Bi 0.72 Fe 4.3 Ga 0.7 O 12 (TBIG) heterostructure. TBIG nanostructured films were sputtered on 300 nm liquid phase epitaxy Y 3 Fe 5 O 12 films at 400 °C and post-annealing in air at 800 °C. X-ray diffraction (XRD) patterns provide evidence of strain-induced lattice mismatch between the Y 3 Fe 5 O 12 and the TBIG films. Strain-induced anisotropy produces multipeak ferromagnetic resonance spectra from the Y 3 Fe 5 O 12 film, and these resonance modes behave differently. Fitting of f - H r data to the Kittel equation yields the anisotropy fields of each resonance mode, indicating the existence of an out-of-plane anisotropic field which is up to 220.9 Oe. We also observe comb-like spin wave spectra causing by the interaction of elastic waves and spin waves in the in-plane and out-of-plane magnetization with peak separation Δ f ≈ 3.24 MHz. [ABSTRACT FROM AUTHOR]