Ferromagnetic Resonance Linewidth Research Articles

Effect of annealing temperature on crystallographic texture, magnetic and microwave properties of barium ferrite thin films

Abstract Due to it has large saturation magnetization (Ms), high magnetocrystalline anisotropy field and high ferromagnetic resonance (FMR) frequency. Barium ferrite (BaM) has attracted more and more attentions in the fields of magnetic recording media, permanent magnets and microwave devices. Here, BaM thin films were deposited on Pt-coated Si substrate, and the effect of annealing temperature on the microstructure and magnetic and microwave properties of barium ferrite thin films in detail. It is found that when the BaM thin film was annealed at 1035°C, it has good properties. The XRD data provide clear evidence that the BaM thin films have high c-axis orientation, and the Lotgering factor is as high as 0.96. The AFM morphology show that BaM grains are out of the film plane, and there are hexagonal. The magnetic hysteresis curves indicated that Both saturated magnetization (4πMs), remanence ratio and OP coercive (Hc) increase with increasing Ta, and get the maximum value at 1035 °C. The ferromagnetic resonance (FMR) measurement show that the FMR linewidth is 143 Oe@50 GHz, it means that this this sample has low microwave loss in millimeter wave loss. These results make sure that this BaM thin film is possible use in millimeter wave devices such as filers, circulators and isolators. 

Phase composition, microstructure, and gyromagnetic properties of LiZnTi ferrites sintered at low temperature

In this study, a series of Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites were successfully synthesized by solid-state reaction method at 920 ℃ employing low melting point V2O5 as sintering aid. The X-ray diffraction (XRD) studies demonstrated that all samples exhibited spinel phase. Microscopic image analysis revealed that both the grain growth and uniformity were significantly promoted. The average grain size was increased from 0.65 µm to 4.53 µm when V2O5 was increased from 0.0 wt% to 2.4 wt%. In terms of the magnetic properties, the saturation magnetization (4πMs) of the samples increased from 2915 Gs to 3434 Gs, the coercivity (Hc) decreased from 848.3 A/m to 242.2 A/m, and the ferromagnetic resonance linewidth (ΔH) decreased from 963 Oe to 543 Oe. It could be noted that the proper addition of V2O5 is the key to optimizing the microstructure and magnetic properties of LiZnTi microwave ferrite. Therefore, as an effective additive, V2O5 can promote the development of low temperature co-fired ferrites.

Mechanism of the impact of Ca–Ge co-substitution on the FMR linewidth in BiV-YIG ferrites

Yttrium Iron Garnet (YIG) ferrites, characterized by their superior magnetic and dielectric attributes, are instrumental in advancing the development of microwave devices, particularly in enhancing high-frequency performance, integration, and miniaturization. This paper synthesizes YIG ferrite materials with the composition Bi0.6Y1.4-xCa1+xFe4.5-xV0.5GexO12 (x = 0.10 to 0.50, incrementing by 0.10) through the solid-state sintering method. It delves deeply into the mechanism by which Ca2+-Ge4+ ions substitution regulates the magnetic properties of BiV-YIG. The microstructural and magnetic properties of the samples were systematically tested and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), vibrating sample magnetometry (VSM), and TE106 perturbation method. At a substitution content of x = 0.50, the substitution of Ge4+ ions for the Fe3+ ions at the d-site transforms the material from ferrimagnetic to paramagnetic, and the saturation magnetization of the sample drops to 132.74 G. By calculating the ferromagnetic resonance (FMR) linewidth using the law of approach to saturation, the study elucidates the negative impact of low saturation magnetization on FMR linewidth. The mechanisms proposed in this paper provide theoretical and experimental bases for reducing the FMR linewidth of high dielectric constant Bi-substituted YIG, paving the way for developing high-dielectric, low-loss YIG ferrite materials for microwave devices.

Spin dynamics of room temperature van der Waals (vdW) ferromagnets and their usage in microwave devices

Quasi-two-dimensional van der Waals (vdW) materials exhibiting room-temperature (RT) long-range ferromagnetic nature have emerged as a significant research field to explore fundamental condensed matter physics due to their intriguing physical properties. These vdW materials enable a futuristic platform for implementing novel spintronics devices. Here, we examined the spin dynamics of polycrystalline Fe5GeTe2 and Fe4.8Co0.2GeTe2 vdW materials using ferromagnetic resonance (FMR) spectroscopy. Vibrating Sample Magnetometer (VSM) study reveals that both materials have a soft ferromagnetic character at room temperature. From room temperature FMR measurements, the effective magnetization of Fe5GeTe2 and Fe4.8Co0.2GeTe2 derived ∼0.54 ± 0.056 and 0.50 ± 0.017 kOe, respectively. These results are consistent with reported VSM data. Fe5GeTe2 and Fe4.8Co0.2GeTe2 exhibit broad FMR linewidths of 0.697 ± 0.036 and 0.748 ± 0.056 kOe, respectively, which can be due to inhomogeneous line broadening. Besides its intrinsic contribution to linewidth, it is also affected by extrinsic Gilbert damping (αext). The value of αext is influenced by conflicting intra-band and inter-band electronic transitions, according to Modified Kambersky's theory. Furthermore, the effective Gilbert damping constant (α) obtained is 0.0513 ± 0.0046 for Fe5GeTe2 and 0.0526 ± 0.0031 for Fe4.8Co0.2GeTe2 at RT. Additionally, we developed microwave signal processing devices using these materials and evaluated their functionality both as a microwave band-reject filter and an adjustable phase shifter. The stop-band response was studied across the 5 to 25 GHz frequency range under an applied magnetic field as high as 7 kOe. For these flip-chip-based devices, attenuation is −5 dB/cm for the Fe5GeTe2-based filter and −3.2 dB/cm on sample Fe4.8Co0.2GeTe2 at 6.95 and 5.37 kOe, respectively. The same micro-strip filter was used as a tunable phase shifter in the off-resonance region. The optimal differential phase shift studied for Fe5GeTe2 and Fe4.8Co0.2GeTe2-based phase shifters in the high-frequency region (22 GHz for Fe5GeTe2 and 18 GHz for Fe4.8Co0.2GeTe2) is 23°/cm and 14°/cm, respectively, at high magnetic fields. These versatile devices find integration across a wide spectrum of applications, such as phased-array antennas, radar systems, and wireless communication systems, offering their benefits to diverse fields.

Magneto-optical epitaxial bismuth-substituted yttrium iron garnet thin films on a diamagnetic substrate for low temperature applications

The uprising interest in the integration of the magneto-optical iron garnets into the field of quantum information processing imposes requirements for the damping parameter and optical properties at low temperatures. Typically, high quality iron garnet films are mostly grown epitaxially on the paramagnetic substrates that have rare-earth elements in its composition, which leads to an increase of their magnetic damping at temperatures below 100 K. Here, we epitaxially grew magneto-optical ferromagnetic garnet films on a diamagnetic yttrium scandium gallium garnet substrate to demonstrate narrow ferromagnetic resonance (FMR) linewidth at temperature range from 300 K to 4 K. The maximum Faraday angle measured at wavelength of 660 nm is ΘF = 0.34 ⋅103 deg/cm at 65 K. The FMR linewidth of the iron garnet film gets slightly larger as temperature decreases, but still remains at a level of 35 Oe at 4 GHz even at 4 K. The investigated iron garnet thin films grown on diamagnetic substrates can be successfully implemented in low-temperature technological applications that require low damping and high magneto-optical response.

Perpendicular magnetic anisotropy in Bi-substituted yttrium iron garnet films

Magnetic garnet thin films exhibiting perpendicular magnetic anisotropy (PMA) and ultra-low damping have recently been explored for applications in magnonics and spintronics. Here, we present a systematic study of PMA and magnetic damping in bismuth-substituted yttrium iron garnet (Bi-YIG) films grown on sGGG (111) substrates by pulsed laser deposition. Films with thicknesses ranging from 5 to 160 nm are investigated. Structural characterization using x-ray diffraction and reciprocal space mapping demonstrates the pseudomorphic growth of the films. The films exhibit perpendicular magnetic anisotropy up to 160 nm thickness, with the zero-magnetic field state changing from fully saturated for low thicknesses to a dense magnetic stripe pattern for thicker films. The films show a ferromagnetic resonance (FMR) linewidth of 100–200 MHz with a Gilbert damping constant of the order of 4×10−3. The broad FMR linewidth is caused by inhomogeneities of magnetic properties on micrometer length scales.

Lowered ferromagnetic resonance linewidth and enhanced spin wave linewidth of nickel-based ferrite ceramics using hot-pressing method

Previous investigations commonly employed solid-state sintering to fabricate Ni-based ferrite ceramics to improve magnetic performance. A few researchers used the hot-pressing method to prepare Ni-based ferrites, but their porosity remained relatively high values (>2%), resulting in high ferromagnetic resonance line widths (ΔH). To date, the influence of high-temperature and high-pressure forming processes on ΔH and spin wave line width (ΔHk) in Ni-based ferrite ceramics has been rarely reported using hot pressing. This study utilized a uniaxial hot-pressing method and systematically investigated the effect of porosity, grain size and grain uniformity on the magnetic properties of Ni-based ferrite ceramics. Porosity played a crucial role in determining ΔH at different sintering temperatures. As the sintering temperature increased, the reduced porosity resulted in a decrease in ΔH. Under varying sintering pressures, the grain uniformity primarily affected ΔH. Increasing pressures led to more uniform grains, causing a decrease in ΔH. The ΔHk was directly associated with the grain sizes. With the increase of sintering temperatures, the grain sizes increased, leading to a decrease in ΔHk. Conversely, as the pressure increased, the decreased grain sizes brought the increased ΔHk. Compared to other hot-pressing results on the Ni-based ferrite ceramics, the optimized high-temperature and high-pressure processing with annealing significantly reduced the porosity of Ni-based ferrite ceramics (0.11%). In comparison with the solid-state sintering without pressures, the optimized hot-pressed Ni-based ferrite ceramics exhibited a 7% increase in saturation magnetization, a 63% reduction in ΔH and a 6.5% increase in ΔHk. The striking reduction of ΔH suggests that microwave devices assembled from Ni-based ferrite ceramics could withstand high power levels while minimizing lower electromagnetic losses, predicting promising applications for Ni-based ferrite materials in high-power microwave ferrite devices.

Investigation of crystal structure, Raman spectroscopy and magnetic properties of La-Zn substituted oriented M-type hexagonal barium ferrites

M-type hexagonal barium ferrite (BaM) has received much attention in the application of self-biased microwave devices because of its large anisotropic field (Ha) and high saturation magnetization (Ms), but the increased Ha inevitably increases the microwave magnetic loss of the device. In addition, the devices need to have a high Ms for high frequency applications. To address these issues, we used La3+ and Zn2+ instead of Ba2+ and Fe3+ ions to modulate the Ha and Ms of BaM, respectively. Ba1-yLayFe12-xZnxO19 (x=y=0.1–0.5) M-type hexagonal ferrite was synthesised by conventional solid-phase methods. The La-Zn co-substituted BaM samples were shown to be purely single phase by X-ray diffraction (XRD) analysis. The lattice parameters, specific surface area, crystallite size, dislocation density and microstrain of the samples were also calculated using the XRD data. Furthermore, La3+ and Zn2+ can not only modulate the sample Ha and Ms between 10,214–12,102 Oe and 62.94–78.23 emu/g, respectively, while making the sample more denser. At x=0.3 BaM detects relatively satisfactory properties: large Ms=63.12 emu/g, suitable Ha=10,214 Oe and Hc=2248.87 Oe, high Mr/Ms=0.832 and narrow ferromagnetic resonance linewidth (= 903 Oe), which provide good candidates for next-generation self-biased and low-loss microwave wave devices.

Growth and microwave properties of layered ferrogarnet structures

The ferrogarnet structures consisting from one- to three- layers of monocrystalline yttrium-iron garnet Y3Fe5O12 (YIG) films, two- layered YIG - La,Ga:YIG and two- layered {Y,Sm,Lu}3(Fe,Ga)5O12 -YIG  structures were grown by liquid-phase epitaxy (LPE) method on gadolinium - gallium garnet Gd3Ga5O12 (GGG) substrates of (111) orientation. The obtained layered ferrogarnet structures were studied by the methods of ferromagnetic resonance (FMR) and magnetostatic wave (MSW) interference. The two- and three- layered YIG structures have a wide FMR line width (∆H). For the three- layered YIG structures with the total thickness of 68-102 μm ∆H = 5,7- 11,5 Oe. The line width ∆H = 0,34 – 1,22 Oe correspond to the two- layered (Y,Sm,La)3(Fe,Ga)5O12 – YIG structures with thicknesses from 3 to 65 μm. Individual layers in all structures are characterized by similar or different saturation magnetizations (4πMs).The frequency MSW separation in the YIG - La,Ga:YIG layered structure was observed. It was shown that the propagation losses of MSW in one- and two- layered structures increase with decreasing wavelength of MSW and transition to a two- layered structure.

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.

Ca-Sn co-substituted BiIn-YIG ferrite with narrow FMR linewidth for microwave device application

The requirements for improving the performance and miniaturizing microwave devices have led to higher demands for the yttrium iron garnet (YIG) ferrite materials. To achieve YIG ferrite materials with narrow ferromagnetic resonance (FMR) linewidths, and stable magnetic and dielectric properties, Ca-Sn co-substituted YIG samples with the composition Bi0.4Y2.6-xCaxFe4.65-xIn0.35SnxO12 were synthesized via solid-state sintering at 1230 °C. The microstructural, magnetic, and dielectric properties of the samples were systematically tested and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), impedance analyzer, vibrating sample magnetometry (VSM), and ferromagnetic resonance (FMR). The results indicate that the co-substitution of Ca2+ and Sn4+ ions did not alter the crystal structure of YIG ferrites, and effectively improved the microstructure and performance of the material. When the doping concentration (x) was 0.40, the obtained sample exhibited the narrowest FMR linewidth (ΔH = 43.46 Oe) and excellent magnetic and dielectric properties (4πMs = 1555.68 G, ε′ = 14.12 @ 100 MHz). The material proposed in this study demonstrates significant potential for applications in microwave devices.

Temperature Dependence of Magnetization Dynamics in Co/IrMn and Co/FeMn Exchange Biased Structures

Thin film ferromagnet/antiferromagnet (F/AF) exchange biased structures that are widely used in GMR spin valves are considered nowadays as promising systems for antiferromagnetic spintronic and spin-orbitronic devices. Here, the temperature dependences of magnetization dynamics in Co/IrMn and Co/FeMn F/AF structures are investigated using ferromagnetic resonance (FMR) in comparison to a free Co layer. A strong additional decrease in the resonance field was observed in Co/IrMn with a temperature decrease attributed to the rotatable anisotropy increase, which almost vanished at room temperature. In contrast to Co/IrMn, the contribution of the rotatable anisotropy in Co/FeMn is much weaker, even though it exists at RT, it is negative, and slightly varies with the temperature and resonance field shift in Co/FeMn. This is mainly due to unidirectional exchange anisotropy. FMR linewidth for the free Co layer increases with decreasing temperature and is accompanied with a slow relaxation process, while the additional contribution to FMR line broadening in Co/IrMn and Co/FeMn structures is correlated with variation in the exchange anisotropy. The observed results are discussed based on structural and surface morphology and magnetization reversal characterization using X-ray diffraction, atomic force microscopy, and vibrating sample magnetometry data.

Enhanced properties of Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrites co-fired with Bi2O3–B2O3 additive at low sintering temperatures

In this study, Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrites were co-fired with Bi2O3–B2O3 (BB) additive at low sintering temperatures (∼920 °C), and the effects of BB additive on various properties of Li–Zn ferrites were systematically investigated. First of all, the existence of BB additive would not pollute the spinel phases of Li–Zn ferrites, in contrast, it could make the ferrites well-ripened at low temperatures. The micro-morphology results revealed that the introduction of BB additive could significantly promote the grain growth, where the average diameter of grain size increased from 0.81 μm (0.0 wt % BB) to 8.12 μm (0.5 wt % BB), leading to a higher densification degree and density. Owing to the liquid phase formed in the sintering process, magnetic properties of the Li–Zn ferrites were improved with the assistance of BB additive. The saturation flux density (Bs) and saturation magnetization could reach a maximum value of 319.3 mT and 74.2 emu/g, respectively. The coercivity (Hc) and ferromagnetic resonance (FMR) linewidths (ΔH) could reach a minimum value of 176.3 A/m and 243.2 Oe, respectively. Finally, it is noted that the optimal values of these parameters are obtained under the condition of 0.5 wt % BB additive doped, and most magnetic properties would be deteriorated when exceeding the above content. Thus, BB additive is considered as a promising sintering aid for synthesizing Li–Zn ferrites at low temperatures, which will play a vital role in the development of low-temperature co-fired ceramics (LTCC) technology.

Electric field control of the ferromagnetic resonance linewidth in synthetic antiferromagnetic heterostructure

In this study, we present a novel approach to control the microwave properties of a Co/Ru/FeNi film, characterized by strong antiferromagnetic coupling and in plane uniaxial anisotropy. The film is fabricated on a Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ferroelectric substrate using the magnetron oblique sputtering. Our experimental results demonstrate a remarkable non-volatile mediation of the ferromagnetic resonance (FMR) field and linewidth by applying the perpendicular-bias electric field. The observed asymmetric butterfly curve indicates the existence of electric mediation dominated by strain effect. Moreover, we investigate the angular dependence of FMR under different electric field, which reveals changes in magnetic anisotropy including FMR field. Notably, the FMR linewidth exhibits a distinctive four-fold anisotropy. Through microstructure analysis of the film surface, we identify that the origin of this FMR linewidth anisotropy is attributed to the two-magnon scattering induced by the oblique sputtering.

Dielectric and gyromagnetic structure modulations of Zn–Sn codoped yttrium–iron–garnet based on the density‐generalized functional theory and P–V–L bond theory

AbstractHerein, the crystal structure, dielectric properties, and gyromagnetic characteristics of Zn–Sn codoped Y3ZnxSnxFe5−2xO12 (x = 0.0–0.5) prepared using a conventional ceramic process were investigated. According to the first‐principles’ calculations and complex crystal bonding theory, Zn2+–Sn4+ codoping can increase the relative dielectric constant (εr) by enhancing the average ionicity. The x‐ray photoelectron spectroscopy (XPS) and Raman analysis results indicate that an appropriate amount of Zn2+–Sn4+ codoping can help improve the microscopic morphology, maintain the appropriate ratio of divalent iron ions, and reduce the microwave magnetic and electrical losses of YIG ferrites. The optimized microwave properties are as follows. Y3Zn0.3Sn0.3Fe4.4O12 after sintering at 1400°C; εr = 15.6; dielectric loss, that is, tanδε = 4.3 × 10−4; saturation magnetization, that is, 4πMS = 2244 G; ferromagnetic resonance linewidth, that is, ΔH = 37 Oe. These properties can help improve the performance of high‐frequency microwave components by enhancing the properties of ferrite.

Spin pumping into a partially compensated antiferromagnetic/paramagnetic insulator

Spin pumping from a metallic ferromagnet (FM) into an insulating antiferromagnet has been studied across the magnetic phase transition by means of temperature-dependent, broad-band ferromagnetic resonance (FMR) experiments. A set of spin pumping heterostructures consisting of Permalloy (Ni80Fe20) as FM and ZnCo x O with and 0.6 (Co:ZnO) as partially compensated antiferromagnetic insulator has been used for which previous experiments have already pointed out the possibility of the existence of spin-pumping. The present experiments allow to reliably separate the various contributions of the temperature-dependent Gilbert damping parameter to the FMR line-width. A careful analysis of the obtained data demonstrates a significant increase of the temperature-dependence of the Gilbert damping parameter around the magnetic phase transition of Co:ZnO which extends up to room temperature, confirming spin pumping into the fluctuating spin sink of an antiferromagnetic/paramagnetic insulator.

The epitaxial iron-yttrium garnet films with homogeneous properties and narrow FMR line width

The growth of iron-yttrium garnet Y3Fe5O12 (YIG) films with of 1...15 μm thicknesses on single-crystal substrates of gallium-gadolinium garnet Gd3Ga5O12 (GGG) was carried out using the method of liquid phase epitaxy (LPE). The influence of the composition and mass of the charge, the temperature regimes, the rates of movement and the substrate rotation on the films parameters were studied. The layered structure caused by the heterogeneity of the chemical composition in the film thickness was determined and studied The dependence of the degree impurity of Pb2+ and Pt4+ ions in YIG films and their influence on the ferromagnetic resonance (FMR) line width ∆H on the films growth conditions was investigated. It’s shown that in order to obtain by the LPE method the series of defect-free films with low magnetic losses and reproducible parameters, it’s necessary to use melt-solutions of large mass (6...12 kg) and apply their additional mixing during the growth process.

Effect of annealing temperature on the properties of BaFe12O19 thin films deposited on GGG (1 1 1) substrates by pulsed laser deposition

In this work, BaFe12O19 thin films with perpendicular magnetic anisotropy have been deposited on GGG (111) substrates by pulsed laser deposition in an oxygen atmosphere using a KrF excimer laser. The effects of annealing temperature on the microstructural, magnetic, and microwave properties of BaFe12O19 thin films were investigated. It is found that the properties of BaFe12O19 films are very sensitive to the annealing temperature, and excellent films are obtained when the annealing temperature is above 900 °C. X-ray diffraction diagrams show that films annealed at higher temperatures (≥950 °C) have better crystallization and higher perpendicular orientation. Atomic force images show the surface morphology of annealed films above 900 °C to be very smooth, with a minimum roughness of 0.754 nm. Hysteresis loops reveal that the saturation magnetization of the films annealed above 1000 °C is similar to that of bulk barium ferrite, and the maximum value of 4676 Gs is obtained at 1100 ℃. The anisotropy field increases with the increase in annealing temperature, reaching a maximum of 18.0 kOe at 1050 °C. The remanence ratio and saturation magnetization also show an upward trend as the annealing temperature rises. The film annealed at 1100 °C shows a very narrow ferromagnetic resonance linewidth with a width of about 256 Oe at 39 GHz. And the ferromagnetic resonance linewidth of the films decreases as the temperature rises, which means that films annealed at higher temperatures have less microwave loss.

Annealing dependence on magnetization dynamics and two-magnon scattering in Co40Fe40B20 thin films

Investigation of magnetization dynamics of low-damping ferromagnetic layers is of paramount interest for the realization of spin-based electronic devices. Here, we report the effect of surface oxidation on the structural properties, magnetization reversal and spin dynamics of Co40Fe40B20 (CFB) films. X-Ray diffraction results show that both as-deposited and annealed CFB layers up to 250 °C exhibit an amorphous state. Partial crystallization of CoFe is observed in CFB films above 350 °C. Magnetization reversal curves measured using longitudinal magneto-optic Kerr effect indicate a characteristic square loop along the easy axis for all samples. Ferromagnetic resonance (FMR) results show that the resonance field (Hr) shifts due to changes in the structural phase or microstructure. FMR linewidth (ΔH) is linear for both as-deposited and all annealed CFB above 10 GHz, whereas anomalous behaviour in ΔH as a function of frequency is observed below 10 GHz frequency for annealed thin films. The extracted damping parameter manifests extrinsic contributions in the annealed samples compared to the as-deposited. Angular-dependant FMR results show ΔH and Hr exhibit opposite trends in CFB film annealed at 450 °C due to the presence of inhomogeneities. It suggests the signature of two-magnon scattering in the 450 °C annealed CFB. Our systematic study helps in the understanding of the effect of annealing on the crystallinity and magnetization dynamics in CFB thin films.