Low Ferromagnetic Resonance Linewidth Research Articles

In–Sn–Cu co-doped yttrium iron garnet ferrite: Magnetic and dielectric properties

With the miniaturization and integration of electronic components, there has been widespread attention on yttrium iron garnet ferrite (YIG) with high saturation magnetization, high dielectric constant, and low ferromagnetic resonance linewidth. In this work, In–Sn–Cu co-doped YIG ferrite with the chemical formula Y3Fe4.8-xCu0.1Sn0.1InxO12 (x = 0.05, 0.10, 0.20, 0.30) was prepared. The properties of the samples, including their microstructure, crystal structure, magnetic attributes, and dielectric properties, were adjusted through the regulation of the indium doping levels. The microscopic and crystal structures confirm the effective doping of ions in YIG, resulting in an expansion of the lattice parameters. Both the saturation magnetization (Ms) and the ferromagnetic resonance linewidth (ΔH) are influenced by the level of doping. The maximum value of Ms is observed at x = 0.10 (30.86 emu/g), whereas the minimum value of ΔH occurs at x = 0.20 (35 Oe). Additionally, increasing doping concentration also leads to an upward trend in both resistivity and dielectric constant, with the lowest dielectric loss occurring at x = 0.15. This study will provide an effective approach for developing high-performance YIG ferrite that meets the requirements of miniaturization and integration.

Effects of Bi2O3–CuO additives on microstructure and microwave properties of low-temperature-sintered NiCuZn ferrite ceramics

In this study, (Ni0.2Cu0.2Zn0.6O)1.03(Fe2O3)0.97 ferrite ceramics with low microwave loss were synthesized through low-temperature sintering and doped with low eutectic mixture Bi2O3–CuO. Additionally, the influence of Bi2O3–CuO doping amount on phase composition, microstructure, and microwave performance of NiCuZn ferrite ceramics was systematically explored. It was found that all samples exhibited pure spinel phase. Moreover, scanning electron microscopy analysis revealed that appropriate doping amount of the Bi2O3–CuO mixture promoted grain growth and densification, leading to dense dual microstructure in NiCuZn ferrite ceramics. Notably, this microstructure significantly enhanced microwave properties of the material. For Bi2O3–CuO doping amount of 0.5 wt % and at sintering temperature of 910 °C, the NiCuZn ferrite ceramics exhibited low ferromagnetic resonance linewidth (ΔH ≈ 90 Oe), minimal dielectric loss (tanδε ≈ 2.73 × 10−4) at 9.3 GHz, and high saturation magnetization (4πMs ≈ 3644 Gauss). These results highlight the potential of Bi2O3–CuO as promising sintering aid, which could support the application of NiCuZn ferrite ceramics to microwave devices.

Gyromagnetic properties of Cu-substituted NiZn ferrites for millimeter-wave applications

In this work, NiCuZn ferrites with different CuO contents were prepared by solid-state method. The influences of the divalent Cu2+ on the crystal structure, microstructure and magnetic properties of NiCuZn ferrite were studied in detail. X-ray diffraction characterization showed that Cu2+ may either replace Ni2+ and enter into crystal lattice, or distributed at grain boundaries in the form of compound. SEM results showed that adding appropriate amount of CuO can promote grain growth and prepare dense NiCuZn ferrites. Especially, the density of the ferrite sample reaches its maximum value of 5.23 g/cm3 when the amount of CuO is 0.20. However, superfluous Cu2+ exists in the form of liquid phase at local grain boundaries once the content of Cu2+ reached 0.25. Moreover, the magnetic hysteresis loops revealed that the specific saturation magnetization first increased and then decreased and the highest value of 76.6 emu/g was obtained at x = 0.10. Consequently, a NiCuZn ferrite with an appropriate microstructure and with high density (5.16 g/cm3), high saturation magnetization (76.0 emu/g), low ferromagnetic resonance (FMR) linewidth (160 Oe) and 4πMs (4930 G) could be obtained at a Cu content of x = 0.15.

Features of the composition and magnetic properties of composites based on ultrafine particles NiFe<sub>2</sub>O<sub>4</sub> produced under low-temperature underwater plasma

The results of studies of NiFe2O4 and ε-Fe2O3 nanoparticles synthesized in a low-temperature underwater plasma are presented. The results obtained indicate the possibility of synthesizing nanocomposites with a given ratio of nickel ferrite, which provides low ferromagnetic resonance linewidths, and ε-Fe2O3, which exhibits high-frequency resonance in the millimeter range of electromagnetic radiation.

A sintering strategy for lithium zinc ferrite with a high saturation magnetization and low ferromagnetic resonance line-width

Based on the activation energy and diffusion kinetics theory of grain growth, Li0.42Zn0.28Ti0.1Fe2.2O4 ceramics with a low ferromagnetic resonance line-width (ΔH) and high saturation magnetization (Ms) were synthesized by adopting LTCC (low-temperature cofired ceramics) technology. The critical sintering temperature of ferrite synthesis was reduced to 925 °C due to activation energy reduction and the liquid phase sintering mechanism of Bi2O3. The sintering agent B2O3 further improved the grain size, homogeneity, density and properties. EDS and XRD refinement showed that Bi3+ and B3+ ions did not enter lattices, but Ti4+ ions entered lattices and replaced part of the Fe3+ ions, leading to the lattice expansion. Finally, homogeneous and compact Li0.42Zn0.28Ti0.1Fe2.2O4 ferrite with Ms up to 354.6 kA/m and ΔH as low as 184.2 Oe was synthesized at temperatures as low as 925 °C by adding an appropriate content of Bi2O3 and B2O3. In the present study, the exploration and practice of reducing the sintering temperature and improving the material properties based on sintering agents is a beneficial supplement and improvement to the wider application of the LTCC technique.

Nb5+ ion substitution assisted the magnetic and gyromagnetic properties of NiCuZn ferrite for high frequency LTCC devices

Nowadays, developing nickle zinc ferrites with excellent magnetic and gyromagnetic properties are of great importance for solving the matching problem of 5G communication system. However, much is discussed about soft magnetic properties, but little is reported gyromagnetic properties that is critical for microwave device applications. Herein, Nb5+ ions substituted Ni0.29Cu0.18Zn0.53NbxFe2-xO4 (x = 0.00-0.05), possessing high saturation magnetization, approriate initial permeability, high cut-off frequency and low ferromagnetic resonance linewidth (@9.55 GHz), were synthesized by low-temperature firing (900 °C). The phase structure and morphology evolutions were studied in detail. The results of morphology observations revealed that Nb5+ substitution has significant role in determining produce compact and uniform microstructures of NiCuZn ferrites via suppress the grain growth, which further corresponding enhance the magnetic and gyromagnetic properties. As a result, a uniform and compact grain size can be obtained, corresponding to the change of magnetic and gyromagenetic properties have different trends. Enhanced magnetic and gyromagnetic performance including high initial permeability (μ' = 203 @1 MHz), saturation magnetization (4πMs = 3966 Gauss) and low ferromagnetic resonance linewidth (ΔH = 203 Oe) of the NiCuZn ferrites is achieved though adjusting Nb5+ ions substitution. More importantly, this work not only for low temperature co-fired ceramic (LTCC) technology but also for high frequency and microwave frequency devices including phase shifter and radars.

C-axis oriented polycrystalline BaNi2GdxFe16-xO27 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) for the application of self-biased circulator at K band

The grains of oriented W-type hexaferrite BaNi2GdxFe16-xO27 (BaW) where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 grew uniformly along their c-axis perpendicular to the sample plane, which meant high remanence ratio of BaW. When Gd3+ substitution content was x = 0.0, the corresponding remanence ratio reached as high as 0.90. When x = 0.2, the oriented BaW simultaneously possessed high saturation magnetization (Ms= 58.36 emu/g), high coercivity (Hc = 1527 Oe), high remanence ratio (Mr/Ms = 0.85), relatively low magnetocrystalline anisotropy field (Ha = 10,253 Oe) and low ferromagnetic resonance linewidth (ΔH = 624 Oe). These characteristics indicated the material was suitable for the design of self-biased circulator operated at K band. Based on the BaW material, self-biased double Y-junction microstrip circulator was designed and realized well circulatory function at K band.

Influences of different Bi2O3 additive amounts on static magnetic characteristics, micromorphology and ferromagnetic resonance linewidth of M-type Sr hexaferrites

Considering the improvement of electronics regarding high frequency and miniaturization, SrM hexaferrites need to exhibit high anisotropy field Ha, high remanence ratio Mr/Ms, and low ferromagnetic resonance linewidth ΔH 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 Ha, high Mr/Ms, and low ΔH. However, it is hard to meet these requirements. In this study, Sr0.4La0.3Ca0.3Fe11.85Al1.0Co0.15O19 was used to study the effect of different doping amounts of Bi2O3 on its magnetic characteristics, micromorphology and FMR linewidth. With the increase of Bi2O3 doping, the grain size of the sample gradually increased, and the uniformity of the grain size gradually decreased. When the Bi2O3 doping amount x increased from 0 to 1.2 wt%, the 4πMs and 4πMr values increased and the coercivity displayed the opposite tendency. The samples showed great uniaxial anisotropy. The magnetocrystalline anisotropy field Ha shows a trend of initially decreased and then increased. When x = 1.0 wt%, Ha reaches the maximum value of 28.9 kOe. At this time, the ferromagnetic resonance linewidth ΔH of the sample is 1578 Oe. The theory of IGA was adopted to divide the FMR linewidth into two parts ΔHa and ΔHp. Accroding to the results, ΔHa takes the bigger proportion of linewidth. However, the change in ΔHp is not negligible. When x = 1.0 wt%, the sample showed its best performance (4πMs = 3412 Gs, 4πMr = 2905 Gs, Hc = 2649 Oe, Mr/Ms = 85.1%, large Ha = 28.864 kOe, and ΔH = 1578 Oe). The SrM ferrite materials provided in this study can potentially be used in the microwave engineering, high-frequency, and self-biased devices.

Investigation on growth mechanism and gyromagnetic properties of low-sintered Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite doped with Nb2O5 and glass sintering additives

Interest in improving the magnetic properties by co-doping has thrived since it is demonstrated that such co-doping can be used to control the microstructure of ferrites at a low sintering temperature. Usually this process involves grain growth and densification by liquid phase sintering or, in some cases, abnormal growth of grain. Here, we study the growth mechanism of the low-sintered LiZnTi ferrites doped with additions of Nb2O5 and Li2CO3-MgO-ZnO-B2O3-SiO2 (LMZBS) glass through characterization of microstructure and magnetic properties. SEM results show that along with the increase of LMZBS glass contents, the change of ferrite grain presents three different stages. At the initial stage, densification of grain is dominant and grain growth is unconspicuous. Due to the increase of LMZBS glass content, the main process at the second stage is grain growth. At the last stage, however, grain growth starts to be suppressed and pores appear again because of competition between the two additives. Corresponding to each stage, the magnetic parameters of the LiZnTi ferrites, including 4πMs, Hci, Bs, Br/Bs and ΔH, have different trends. Moreover, XRD patterns show that all samples have a pure spinel phase, which means influence of the two additives on crystal structure is negligible. All in all, we obtain a LiZnTi ferrite with uniform and compact microstructure, high saturation flux density (Bs=294.2mT), remanence ratio (Br/Bs=0.87), saturation magnetization (4πMs=3700.1 G) and low ferromagnetic resonance linewidth (ΔH=253) at 900 °C.

Study on structure, magnetic and dielectric properties of li-Zn ferrite with low ferromagnetic resonance line-width and high saturation magnetization synthesized at low temperature by LTCC

Spinel structure Li0·43Zn0·27Ti0.13BixFe2.17-xO4 (x = 0 or 0.003) ceramic with high saturation magnetization (Ms) and low ferromagnetic resonance line-width (nH)was successfully prepared by low temperature co-fired ceramic (LTCC) technology adoping Bi2O3 as active agent and B2O3 as sintering agent. Crystalline structure analysis was performed by XRD, and results show that Bi3+ entering the lattice replaces Fe3+ at B site on octahedral or tetrahedral crystal structure, resulting in lattice expansion and overall left shift of diffraction peaks. Based on SEM, the principle of Bi2O3 and B2O3 promoting sintering is analyzed, and the mechanism of this process is illustrated by a diagrammatic model. The reason of high Ms and low nH is revealed by VSM, which is attributed to the decrease of activation energy and the effect of sintering agent on grain boundary diffusion and grain growth. Dielectric properties were investigated, and it is found that the dielectric constant (ε´) is affected by grain size, defect, grain boundary, doping and usage frequency, etc., and the reason and law of the influence are explored by space charge polarization theory. Finally, by adding the optimal amount of Bi2O3 (x = 0.003) and B2O3 (y = 0.6), a LiZnTi ferrite with a low ferromagnetic resonance line-width (nH as low as 181.6 Oe) and a high saturation magnetization (Ms up to 353.1 kA/m) was successfully prepared at a low temperature (915 °C) by LTCC.

Effects of La substitution on micromorphology, static magnetic properties and low ferromagnetic resonance linewidth of self-biased M-type Sr hexaferrites for high frequency application

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 Mr/Ms, a high anisotropy field Ha, and a low ferromagnetic resonance (FMR) linewidth ΔH 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 Mr/Ms, high Ha, and low ΔH, 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 ΔH 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 4πMs and coercivity Hc initially increased, and then decreased. The Ha values of all samples were higher than 18 kOe. The FMR linewidth ΔH 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 ΔHa accounted for a larger proportion of the FMR linewidth than the porosity linewidth ΔHp. The sample with a La substitution content x of 0.3, exhibited the best performance (4πMs = 3915 Gs, 4πMr = 3387 Gs, Hc = 1818 Oe, Mr/Ms = 0.865, large Ha = 23.99 kOe, and ΔH = 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.

Regulation of Microstructure, Static, and Microwave Magnetic Performance of NiFe/FeMn/NiFe Heterogeneous Multilayer Films Based on Thickness of FeMn Films

Ferromagnetic (FM)/antiferromagnetic (AFM) heterogeneous multilayer films have triggered tremendous interests for application in microwave/mm devices and components. However, with the development trend of miniaturization, high frequency, and lightweight of devices, the FM/AFM heterogeneous multilayers are desired to possess high saturation magnetization (4πMs), low coercivity (Hc), and low ferromagnetic resonance (FMR) linewidth (∆H). Herein, the Ni81Fe19 (50 nm)/Fe50Mn50 (t nm)/Ni81Fe19 (50 nm) films were fabricated by DC magnetron sputtering, and the effects of thickness of the Fe50Mn50 on the microstructure, static, and microwave properties were investigated in detail. With increasing the FeMn film thickness, the saturation magnetization firstly increased and then decreased from 7947 to 9448 Gs. The in-plane coercivity firstly decreased and then increased from 28.58 to 0.6115 Oe, and the out-of-plane exchange bias field undergoes a transition from a negative exchange bias to a positive exchange bias. Besides, the ferromagnetic resonance linewidth firstly decreased and then increased from 142 to 87 Oe. Remarkably, with a 15-nm Fe50Mn50 film, the heterogeneous multilayer films achieved optimum performance with high saturation magnetization (9448 Gs), low coercivity (1.02 Oe), and low FMR linewidth (94 Oe). The outstanding Ni81Fe19/Fe50Mn50/Ni81Fe19 heterogeneous multilayer films exhibit great potentials in radar remote sensing, communication, and electronic countermeasure fields.

Magnetic properties study of spin pinned NiFe/FeMn/NiFe heterogeneous multilayer films with different NiFe thicknesses

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.

Discussion of strong pinning effect via nonuniform PSSW mode in Fe/NiFe/Fe multi-layer films with different Fe film thicknesses

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)/Ni81Fe19 (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 (Hp) increased from 133 to 379 Oe, and the perpendicular standing spin-wave linewidth (ΔHp) increased from 68 to 148 Oe. Remarkably, with 8 nm thick Fe film, the multilayer films achieved excellent comprehensive performances with high saturation magnetization (4πMs, 13,525 Gs), a low in-plane ferromagnetic resonance field (Hr, 725 Oe), and a low FMR linewidth (ΔH, 84.24 Oe).

Grain growth and tunable ferromagnetic resonance linewidth of low-temperature sintering NiCuZn gyromagnetic ferrites

NiCuZn (NCT) ferrites-based ceramics material have received significant attention for good gyromagnetic properties in recent years. Densification and ferromagnetic resonance linewidth play a critical role in modern system including circulators, phase shifters. However, there are still technological challenges associated with its application to achieve high-performance communication system. In this work, we have carried out a analysis of the influence of sintering temperature and time on the dependent structural, tunable gyromagnetic properties of NCZ ferrites. SEM results found that a direct consequence of varying the sintering temperature and time to be on the variation in the grain size, thus adjusting the ferromagnetic resonance linewidth of NCZ ferrites. We also found that sufficient grain growth is adversely affect ferromagnetic resonance linewidth. Finally, uniform and compact NCZ gyromagnetic ferrites were successfully synthesized at a low temperature (~ 880 °C for 3 h). The fine microstructure of NCZ ferrites sintered at 880 °C for 3 h also possessed excellent gyromagnetic properties (high 4πMs≈ 3400.29 Gauss, and low ΔH ≈ 158.39 Oe). It was indicated that this greatly low ferromagnetic resonance linewidth of NiCuZn ferrites can be utilized for new generation high-performance microwave devices.

Effects of Bi2O3–CaCu3Ti4O12 composite additives on micromorphology, static magnetic properties, and FMR linewidth ΔH of NCZ ferrites

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 4πMs, low coercivity Hc, and low ferromagnetic resonance (FMR) linewidth ΔH. Herein, 0.1 wt% Bi2O3 and 0.0–3.5 wt% CaCu3Ti4O12 (CCTO) composite additives were introduced to NCZ ferrites, the influence of Bi2O3–CCTO composite additives on micromorphology, static magnetic properties, and FMR linewidth ΔH of NCZ ferrites have been demonstrated in detail. The results show that increasing the CCTO amounts in NCZ ferrites, saturation magnetization 4πMs monotonically decreases from 5484Gs to 4819Gs, and both coercive force Hc and FMR linewidth ΔH 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 ΔH to the crystalline anisotropy linewidth ΔHa and porosity induced linewidth ΔHp. The sample with 0.1 wt% Bi2O3 and 1.5 wt% CCTO possesses high saturation magnetization 4πMs (5321Gs), remanence Br (200 mT), low coercivity Hc (31A/m), and low FMR linewidth ΔH (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.

Structure and magnetic properties of In-substituted MgCd ferrite material

In this paper, low temperature co-fired In-substituted MgCd ferrites (Mg0.8Cd0.2Fe2-xInxO4, x = 0.00, 0.05, 0.10, 0.15) were synthesized by traditional solid state method. XRD showed that In3+ ion not changed phase formation in low doped content. Grain size had obvious changes due to In3+ ions. Under In3+ ion doping, magnetic hysteresis loops showed both saturation magnetization (Ms) first increased and then decreased, and the maximum value was 33.2 emu g−1 (x = 0.10). Coercivity (Hc) decreased first to minimum value(51.99 Oe @x = 0.10) and then increased. The ferromagnetic resonance (FMR) linewidth (ΔH) of samples were tested at 9.56 GHz, and the results showed that the low FMR linewidth was 219.7 Oe when In-doped content was 0.10. the excellent magnetic properties (ΔH, 219.7 Oe @9.56 GHz, Ms, 33.2 emu g−1, Hc, 51.99 Oe) showed that the materials have potential for use in high frequency self-biased microwave electronic devices such as phase shifter or circulators.

Microstructures and magnetic properties of low temparature sintering NiCuZn ferrite ceramics for microwave applications

Polycrystalline (Ni0.2Cu0.2Zn0.6O)1.03(Fe2O3)0.97 (NiCuZn) ferrite ceramics with low ferromagnetic resonance (FMR) line width (ΔH) and high saturation magnetization (4πMs) were synthesized at low sintering temperatures by adding Bi2O3–ZnO–B2O3 (BZB) glass additives. Furthermore, phase compositions, microstructures, and magnetic properties of the low-temperature-sintered NiCuZn ferrite ceramics were systematically analyzed. First, X-ray diffraction patterns showed that BZB glass has no obvious effect on phase structure of NiCuZn ferrites. Moreover, scanning electron microscopy images revealed that BZB glass can dramatically enhance grain growth and densification of the ferrites. More importantly, due to grain growth and reduction of porosity, ΔH of the NiCuZn ferrite sintered at 870 °C decreased significantly from 521.2 Oe to 150.5 Oe. Moreover, compact and uniform NiCuZn ferrites possessed high saturation magnetization (4πMs = ~4267 Gauss), reduced coercivity (Hc = ~92.2 A/m), and large saturation flux density (Bs = ~269.1 mT). The above mentioned results indicated that low-melting point BZB glass is an optional sintering aid to promote grain growth and enhance gyromagnetic properties of NiCuZn ferrites sintered at low temperature.

Synthesis of lithium zinc ceramics with a high saturation magnetization and a low ferromagnetic resonance line-width via two-step sintering strategy using low temperature co-fired ceramic technology

Abstract Lithium zinc ferrite (Li0·435Zn0·26Mn0·06Ti0.1BiyFe2.155-yO4) with a high saturation magnetization (Ms) and a low ferromagnetic resonance line-width ( Δ H ) was successfully synthesized by Low Temperature Co-Fired Ceramic (LTCC) technology using a two-step sintering strategy. In the pre-sintering stage, the optimal amount of active agent (Bi2O3) was added to LiZnMnTi ferrite to reduce reaction activation energy and promote grain growth at low temperature. SEM revealed that active agent effectively reduced critical sintering temperature to 920 °C and promoted grain growth at low temperature. During the final sintering process, various amount of V2O5 additive was added to make up the defect of asymmetrical grain growth caused by imbalances between grain growth and boundary diffusion from the influence of Bi2O3. It not only further promoted grain growth, but also greatly improved grain uniformity, reduced defects and increased material density. Finally, LiZnMnTi ferrite with a high Ms (353 kA/m), a low Δ H (182Oe), and a large average grain size (∼8 μm) was successfully synthesized by adding an optimal amount of V2O5 (0.6 wt%).

Low-loss YIG thick films for microwave applications

We report the fabrication, densification and characterization of polycrystalline free-standing yttrium iron garnet Y3Fe5O12 (YIG) thick films in this paper. The thick films were fabricated using a double doctor blade technique from co-precipitated nanocrystalline YIG powders. The sintering temperature of YIG thick films was varied from 1000 to 1400°C. A volume diffusion mechanism is seen to govern the densification process. A high relative density of ~99% could be achieved in a YIG thick film, with a thickness of 80 µm, sintered at a relatively low temperature of 1300 °C. The magnetization value ~1750 Oe, near to the YIG bulk magnetization value and an acceptable low ferromagnetic resonance (FMR) linewidth (∆H) of 80 Oe resulted in these high density YIG thick films with microwave device possibilities.