Resonance Field Hr Research Articles

Effects of interfacial oxygen diffusion on the magnetic properties and thermal stability of Pd/CoFeB/Pd/Ta heterostructure

We investigated the effects of annealing temperatures (TA) on a Pd (5 nm)/CoFeB (10 nm)/Pd (3 nm)/Ta (10 nm) multilayer structure. The as-deposited sample showed an amorphous state with in-plane uniaxial magnetic anisotropy (UMA), resulting in low coercivity and moderate Gilbert damping constant (α) values. Increasing TA led to crystallization, forming bcc-CoFe (110) crystals, which increased in-plane coercivity and introduced isotropic magnetic anisotropy, slightly reducing the α. The two-fold UMA persists up to 600 °C, and the thermal stability of the in-plane magnetic anisotropy remains intact even TA = 700 °C. The TA significantly influenced the magnetic properties such as in-plane saturation magnetization (Ms//), in-plane and out-of-plane coercivities (Hc// and Hc⊥), and in-plane effective magnetic anisotropy energy density (Keff). Above 600 °C, Keff decreased, indicating a transition towards uniaxial perpendicular magnetic anisotropy. Interfacial oxidation and diffusion from the Ta capping layer to the Pd/CoFeB/Pd interfaces were observed, influencing chemical bonding states. Annealing at 700 °C, reduced oxygen within TaOx through a redox reaction involving Ta crystallization, forming TaB, PdO, and BOx states. Ferromagnetic resonance spectra analysis indicated variations in resonance field (Hr) due to local chemical environments. The α reduction, reaching a minimum at 300 °C annealing, was attributed to reduced structural disorder from inhomogeneities. Tailoring magnetic anisotropy and spin dynamic properties in Pd/CoFeB/Pd/Ta structures through TA-controlled oxygen diffusion/oxidation highlights their potential for SOT, DMI, and magnetic skyrmion-based spintronic devices.

Effect of rare earth (Ho and Er) co-substitution on the magnetic and dielectric properties of nanocrystalline cobalt ferrites

Nanocrystalline cobalt ferrites co-substituted with rare earth Ho and Er (CoFe2-2xHoxErxO4, 0 ≤x≤0.10) have been synthesized via the sol-gel method. X-ray Diffraction (XRD) confirmed the single-phase spinel structure with reduced crystallite sizes (65 nm–12 nm), micro-strain (ε) and increased lattice constant (a) with Ho–Er co-substitution. Rietveld refinement and theoretical computation revealed Ho and Er occupancy at octahedral sites and Fe and Co ions redistribution between the tetrahedral and octahedral sites. Infrared spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) supported the formation of the desired spinel structure, aggregated spherical morphology, chemical stoichiometry and elemental states. Magnetic measurements showed a systematic decrease in saturation magnetization (Ms), magnetocrystalline anisotropy (K1), coercivity (Hc) and Curie temperature (Tc) with Ho–Er co-substitution. Electron Spin Resonance (ESR) exhibited asymmetric resonance peaks, reduced resonance field (Hr), linewidth (ΔHpp) and deviation in Lande g values. Impedance spectroscopy revealed two conduction mechanisms (holes and electrons) with distinct activation energies (EaI and EaII). Modulus spectrum analysis confirmed the thermally activated sample-electrode effects and the Nyquist plots indicated the dominant contribution of the grain boundary resistance to the conduction process. A notable enhancement in the dielectric constant (ε′) was observed with Ho–Er co-substitution. The ac conductivity (σac) followed the Jonscher Power Law (JPL). The temperature-dependent frequency exponent s(T), suggests the existence of two conduction mechanisms: non-overlapping small polaron tunneling (NSPT) and correlated barrier hopping (CBH).

Dzyaloshinsky–Moriya Interaction Induced Anomalous g Behavior of Sr2IrO4 Probed by Electron Spin Resonance

Among the 5d transition metal iridates, Sr2IrO4, which has a layered chalcogenide structure, has received much attention due to its strong spin–orbit coupling (SOC), which produces Mott insulating states and anomalous physical behaviors. In this paper, the microscopic magnetism of Sr2IrO4 is studied with electron spin resonance (ESR) measurements. The Lande factor g of the ferromagnetic resonance signal of Sr2IrO4 shows anomalous behavior compared to typical ferromagnets. It gradually decreases, and the corresponding resonance field Hr increases, with decreasing temperature. The various physical parameters. including the saturated magnetic field Hs derived from M-H, Hr, ΔHpp, the g factor and the intensity I extracted from ESR spectra, are analyzed in detail. Eventually, it is revealed that the anomalous behavior of the g-factor is induced by in-plane Dzyaloshinsky–Moriya interaction (DMI) rather than the SOC effect.

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.

Influence of RE-Gd3+ ion substitution on structure, morphology, optical, and magnetic analysis of Cu-Cd based nano ferrites synthesized by low-temperature citrate sol–gel auto combustion method

The current study focused on the influence on physical, thermal, spectral, optical, and magnetic properties with the replacement of Fe3+ ions by large ionic radii rare-earth Gd3+ ions in CuCdFe2O4 nano-ferrites. The Gd3+ doped CuCdFe2O4 ferrite samples with chemical composition Cu0.8Cd0.2GdxFe2-xO4 (x = 0, 0.025, 0.05, 0.075 and 0.1) were produced by citrate sol–gel auto combustion route from the metal nitrates of the corresponding compounds. With the help of Thermo-gravimetric and differential thermal (TG-DTA) analysis, the temperature-dependent spinel phase formation and weight loss percentages were examined. The results of Powder X-ray diffraction patterns and FTIR spectra revealed the development of a cubic single-phase structure with α-Fe2O3 secondary phase, and stretching of metal ion bonds with the addition of Gd3+ ion in CuCdFe2O4 ferrites. From XRD data the observed lattice parameter was in the range of 8.323–8.469 Å and the average crystalline size was increased from 13 to 18 nm. “Field emission scanning electron microscopy” (FE-SEM) and “high-resolution transmission electron microscopy” (HR-TEM) analysis was used to give the particle size, shape, clear agglomeration, and dense structure of Gd3+ doped Cu-Cd nanoparticle. The semiconducting nature of the fabricated samples were confirmed from the characteristic UV–Vis spectra and the respective optical band gap values (1.70–1.74 eV). Electron spin resonance spectroscopy (ESR) analysis was provided the information about the various factors including g-value, peak to peak line width (ΔHPP), resonance field (Hr), and time relaxation (T2). The magnetic characteristic hysteresis loops of synthesised samples at 300 K and 15 K temperatures were obtained by VSM. The results showed that all Gd3+ doped samples exhibited a ferromagnetic nature at 300 K and enhanced hard magnetic nature at 15 K. The maximum saturation magnetisation (MS) was observed for x = 0.025 at both the temperatures (31.66 emu/g at 300 K and 39.65 emu/g at 15 K). The HC values were found in the range of 169.23–557.29 Oe at 300 K and 374.69–749.85 Oe at 15 K. The observed SQR (Mr/Ms) values revealed the single domain structure of prepared samples.

Temperature dependence of magnetic properties and ferromagnetic resonance in oriented hcp CoIr soft magnetic films with/without easy-plane magnetocrystalline anisotropy

The static magnetic properties and ferromagnetic resonance of the c-axis oriented hcp Co0.85Ir0.15 and Co0.98Ir0.02 soft magnetic films, with an easy-plane magnetocrystalline anisotropy (MA) and a c-axis MA, respectively, are investigated with temperature from 300 K down to 5 K. As the MA is opposite, opposite behavior in the temperature dependence of the effective demagnetization field Heff is observed: a decrement in Co0.98Ir0.02 film and an increment in Co0.85Ir0.15 film, respectively. Moreover, the resonance field HR(T) obtained under high frequency is different from that under low frequency for Co0.85Ir0.15 film, which is significantly different from the similar behavior in HR(T) under each frequency (6–18 GHz) for Co0.98Ir0.02 film. The fitting in HR(T) indicates that the opposite MA is also the primary reason for the different appearance in HR(T). Our findings provide supports to develop the advantages and applications of the soft magnetic films with easy-plane MA.

Magnesium and yttrium doped superparamagnetic manganese ferrite nanoparticles for magnetic and microwave applications

Magnesium and yttrium doped manganese ferrite nanoparticles based on chemical formula MgxMn1-xYxFe2-xO4 (x = 0.0, 0.05, 0.10, 0.15) have been prepared by chemical coprecipitation technique and calcined to 600 °C. Thereafter, structural, morphological, optical, magnetic and dielectric investigations were performed. X-ray diffraction (XRD) suggests that the grown composition is cubic spinel. Parameters like crystallite size, lattice parameter, unit cell volume and theoretical density were determined. The crystallite size has been found to decrease from 47 nm to 37 nm for x = 0.0–0.15 respectively. Scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDAX) has been used to investigate the morphology and elemental analysis. The optical band gap calculated using Kubelk-Munk (K-M) method increases from 1.84 eV for x = 0 to 2.35 eV for x = 0.15. The spin characteristics investigated through electron paramagnetic resonance (EPR) spectroscopy gives various parameters like g-value, resonance field (Hr), peak to peak line width (Hpp) and relaxation time (τ2). The value of g is determined and comes out to be 2.086, 2.047, 2.043 and 2.039 for x = 0.0, 0.05, 0.10 and 0.15 respectively. The hysteresis curves obtained using vibrating sample magnetometer (VSM) shows ferrimagnetic behavior of composition. Saturation magnetization (Ms), retentivity (Mr), coercivity (Hc), remenance ratio (Mr/Ms), anisotropy constant (K1) and Bohr magneton number (n) were determined. The value of saturation magnetization decreases from 18.12 emu/g to 7.4 emu/g when the doping concentration increases from x = 0.0 to 0.15. Mr and Hc values are small representing the superparamagnetism. Mr/Ms suggests the single domain structure. The dielectric constant shows frequency dispersion which is typical in spinel ferrites. The value of dielectric constant is high in pure manganese ferrite and decreases with increase in Mg2+ and Y3+ content e.g., at 2.5 kHz the value of dielectric constant is 62 for x = 0.0 and 22 for x = 0.15.

Heusler compound [formula omitted]FeGa nanoarchitectures

Heusler type one-dimensional nanogeometries Ni2FeGa have been fabricated in the nanopores of 150 nm AAO (Anodic Aluminium Oxide) templates using simple and low-cost electrodeposition technique at room temperature. The structure of prepared nanoarchitectures is face centered cubic (fcc) with a secondary γ phase. Magnetic properties have been studied at room temperature as well as at low temperatures. It has been found that saturation magnetization MS decreases as temperature rise up. The nanowires have maintained ferromagnetic behavior from 5 K to 350 K. The Ni2FeGa nanowires (NWs) and nanotubes (NTs) have the same saturation magnetization, the difference of the resonance field Hr is mainly attributed to the difference of the anisotropy field Hk under the fixed microwave frequency. Hr for the NT sample is smaller than that for the NW sample.

Comprehensive study of magnetic and optoelectronic properties of MgFe2O4–TiO2 nanocomposites

Pure MgFe2O4 and TiO2 nanoparticles have been synthesized using co-precipitation and sol-gel method, respectively. A facile ultrasonication method is used to prepare MgFe2O4– TiO2 nanocomposites (NCs) with varying concentration of TiO2. Effect of varying TiO2 concentration in different NCs on microstructural and morphological properties have been investigated using X-ray diffraction (XRD), High Resolution-Transmission Electron Microscopy (HR-TEM) and Fourier transform Infrared (FTIR) analysis. These studies confirm the presence of dominant nanocomposite phases of MgFe2O4 and TiO2 along with two impurity phases, Hematite and Armalcolite, in the synthesized NCs. Impact of TiO2 content and the presence of impurity phases on the magnetic and optoelectronics properties have been discussed comprehensively for future applications. UV–Visible (UV/Vis) and Photoluminescence (PL) spectra yield the band gap of composite to be tuned and quite useful for photocatalytic applications. Magnetic properties of the pure and composite samples are studied using Vibrating Sample Magnetometer (VSM). Further, the electronic and magnetic properties of the powdered samples are explored using Electron Paramagnetic Resonance (EPR) Spectroscopy. Variation in g value, peak-to-peak line width (Hpp), resonance field (Hr) and spin–spin relaxation time (T2) for different samples provide useful information about electronic properties of the composite system.

EPR Spectra of Sintered Cd1-xCrxTe Powdered Crystals with Various Cr Content.

In this paper, we show a simple method of producing ferromagnetic materials with a Curie temperature above room temperature. The electron paramagnetic resonance (EPR) spectra of Cd1−xCrxTe (0.002 < x < 0.08) were measured with a dependence on temperature (82 K < T < 381 K). Obtained EPR lines were fitted to a Lorentz-shaped curve. The temperature dependencies of the parameters of the EPR lines, such as the peak-to-peak linewidth (Hpp), the intensity (A), as well as the resonance field (Hr), were studied. Ferromagnetism was noticed in samples at high temperatures (near room temperature). For a sample with a nominal concentration of chrome of x = 0.05, a very strong intrinsic magnetic field is observed. The value of the effective gyromagnetic factor for this sample is ge = 30 at T = 240 K. An increase of chrome concentration above x = 0.05 reduces the ferromagnetic properties considerably. Analysis of the temperature dependencies of the integral intensity of EPR spectra was carried out using the Curie–Weiss law and the paramagnetic Curie temperature was obtained.

Ferromagnetism in Mn doped 3C-SiC: A variable temperature ESR study

This paper discusses the effect of defects and role of charge carriers in setting up the long range magnetic order in Mn doped 3C-SiC. Using complementary experiments like temperature variation of Electron Spin Resonance (ESR) and DC magnetic susceptibility, the nature of magnetic interactions, spin dynamics and anisotropy have been investigated. The variation of ESR parameters such as, gvalue, peak to peak line width(ΔHpp), spin density (Ns) and spin–spin relaxation time (T2) as a function of temperature and dopant concentration confirms the presence of exchange interaction present in the system. The decrease in resonance field Hr as a function of temperature indicates the strengthening of internal field already existing in Mn doped 3C-SiC samples. This result confirms that defect induced magnetism could be enhanced by introducing holes in to the host wide band gap semiconductor.

Role of Ce concentration on the structural and magnetic properties of functional magnetic oxide particles.

Functional magnetic oxide particles offer exceptional GHz frequency capabilities, which can significantly enhance the utility of communication and signal processing devices. In the present work, we have investigated the structural and magnetic properties of rational multifunctional oxide Y2.9−xCexBi0.1Fe5O12 particles – a full series with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1 via a conventional solid-state route. The X-ray diffraction pattern validated the Ia3̄d cubic garnet phase in all samples. From Rietveld refinement, it is observed that the ceric oxide (CeO2) impurity increases with an increase of Ce concentration, evincing a partial substitution of cerium (Ce) element into the garnet structure. The magnetic oxide particles with Ce concentration x = 0.4 showed a better crystallite size, dodecahedral site occupancy and solubility of cerium in the garnet phase. The morphological visualization of random shaped grains in the micrometer range was performed using the scanning electron microscopy (SEM) technique. The static magnetic properties showed that the saturation magnetization (Ms) decreases up to 43% and coercivity increases up to 59% with the increase of Ce concentration. The dynamic investigation on these oxide particles exhibits various intriguing and novel properties. Various intrinsic material parameters such as saturation magnetization (Ms), gyromagnetic ratio (γ), Gilbert damping constant (α) and extrinsic contribution (ΔHo) to linewidth were determined from the fitting of resonance field (Hr) and field linewidth (ΔHr) data. We ascertained that the damping constant increases with the increase of Ce concentration, which can be explained in terms of two magnon scattering and local defects caused by CeO2 inhomogeneity. The proposed doped garnets can be a potential candidate for high frequency microwave applications and spin-transfer-torque devices.

Converse magneto-electric effects in a core\u2013shell multiferroic nanofiber by electric field tuning of ferromagnetic resonance

This report is on studies directed at the nature of magneto-electric (ME) coupling by ferromagnetic resonance (FMR) under an electric field in a coaxial nanofiber of nickel ferrite (NFO) and lead zirconate titanate (PZT). Fibers with ferrite cores and PZT shells were prepared by electrospinning. The core–shell structure of annealed fibers was confirmed by electron- and scanning probe microscopy. For studies on converse ME effects, i.e., the magnetic response of the fibers to an applied electric field, FMR measurements were done on a single fiber with a near-field scanning microwave microscope (NSMM) at 5–10 GHz by obtaining profiles of both amplitude and phase of the complex scattering parameter S11 as a function of bias magnetic field. The strength of the voltage-ME coupling Av was determined from the shift in the resonance field Hr for bias voltage of V = 0–7 V applied to the fiber. The coefficient Av for the NFO core/PZT shell structure was estimated to be − 1.92 kA/Vm (− 24 Oe/V). A model was developed for the converse ME effects in the fibers and the theoretical estimates are in good agreement with the data.

Controllable electric field tuning of anisotropic magnetic response of Ni/PMN-PT heterostructures

Epitaxial Ni films with various thicknesses were grown on (001)-oriented 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) substrates. Electric field tuning (E-tuning) of ferromagnetic resonance field (Hr) was utilized to investigate the magnetic response of Ni films along different film directions. Butterfly-like Hr vs E curves are shown when magnetic field is applied along film edge. While the combination of both loop-like and butterfly-like Hr vs E curves are observed for Ni film with thicknesses of 180 nm and 240 nm, and merely loop-like curves can be seen for film thicknesses of 330 nm and 510 nm, as magnetic field is applied along film diagonal. These interesting phenomena are assumed to be related to ferroelectric and ferroelastic domain switching in PMN-PT, film strain status, as well as magnetic anisotropy in Ni film. This work demonstrates the feasibility of control of anisotropic magnetic response via electric field in multiferroic heterostructure.

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).

EPR and optical studies of pure MgFe2O4 and ZnO nanoparticles and MgFe2O4–ZnO nanocomposite

A comprehensive EPR and optical studies of pure MgFe2O4 and ZnO nanoparticles and MgFe2O4–ZnO nanocomposite have been done in order to explore its future possibilities of applications. Pure MgFe2O4 and ZnO nanoparticles have been synthesized using Sol–Gel method. MgFe2O4–ZnO nanocomposite has been prepared using water dispersed pure MgFe2O4 nano seeds (previously synthesized) by ultrasonication. Effect of introducing zinc oxide in pure MgFe2O4 nanomatrix on structural properties was investigated using X-ray diffraction and transmission electron microscopy techniques. They confirm the cubic spinel structure of both pure and ZnO imbedded MgFe2O4 samples. UV–Visible and photoluminescence spectra show that the band gap of composite is tuned and more useful for photocatalytic applications. FTIR spectra indicate the presence of absorption bands in the range 390–561 cm−1, which is a common feature of spinel ferrite. The energy dispersive spectroscopy analysis confirms the composition of specimen. Further, the investigation of electronic and magnetic properties of the powdered samples is done using electron paramagnetic resonance spectroscopy. Change in g value, peak-to-peak line width (Hpp), resonance field (Hr) and spin–spin relaxation time (T2) give useful information.

Low-Voltage-Manipulating Spin Dynamics of Flexible Fe3O4 Films through Ionic Gel Gating for Wearable Devices.

Mechanical flexible electronic/spintronic devices have shown enormous application potential to impact our daily life. Here, an in situ low-voltage-controlled flexible field-effect transistor structure was exploited, which consists of a support layer (mica), functional layer (Fe3O4), and control layer (ionic gel). By applying a low voltage (1.5 V) on the ionic gel, the spin-dynamic properties of the function layer were manipulated and a reversible, nonvolatile 345 Oe ferromagnetic resonance field ( Hr) shift was achieved, which corresponds to a large magnetoelectric (ME) coefficient of 230 Oe/V. In addition, a reversible 126 Oe Hr shift (84 Oe/V) was obtained when the layers were bent at curvature radius r = 15 mm. The ME tunability could be attributed to the E-field induced ionic transformation between Fe2+ and Fe3+ at the interface via electrostatic induction. This sandwich structure shows an excellent and effective ionic gel gating system and paves the way for low-voltage-tunable, nonvolatile, and flexible spintronic devices such as memory devices, sensors, and logical devices.

Thickness dependent magneto-static and magneto-dynamic properties of CoFeB thin films

The authors report thickness dependent magneto-static and magneto-dynamic properties of amorphous Co40Fe40B20 films with thickness, t = 10–200 nm deposited on thermally oxidized Si substrates using magnetron sputtering technique at ambient temperature. Magnetic hysteresis loops of films with t ≤ 20 nm transformed from rectangular or flat type shape to transcritical nature for t ≥ 50 nm. This is attributed to a change in the magnetic domain structure from in-plane magnetization with uniaxial anisotropy in thinner films to stripe domains with effective magnetic anisotropy in thicker films. Magnetization dynamics in the films has been investigated using ferromagnetic resonance spectra. Out-of-plane angular dependent resonance field (Hr) and linewidth (ΔH) data have been interpreted using the Smit–Beljers formula. It is found that ΔH contains large extrinsic contribution with the major one being two-magnon scattering. An inverse scaling of Gilbert damping constant (α) with the film thickness over the entire thickness range of 10–200 nm is observed with the lowest α value of 0.004. The results reveal a cost effective strategy for developing films for spintronics based microwave devices and spin-transfer-torque based magnetic devices.

FMR and Magnetic Studies of RF-Sputtered Mn-Zn Ferrite Thin Films

The Manganese–Zinc ferrite (MZF) thin films were deposited on quartz substrates by radio frequency (RF) magnetron sputtering at 10 mTorr of argon gas pressure. The FMR and magnetization measurement were carried out to understand magnetic properties of the as-deposited and annealed MZF films. The resonance field (Hr) of the FMR spectra shifts towards higher magnetic field when angle between applied field and thin film plane is changed from 0 to 90° indicating the existence of uniaxial anisotropy in the film. Whereas, Hr shifts towards lower magnetic field with decrease in temperature of the film. This is due to ferrimagnetic ordering in the films at low temperatures. The magnetization versus field (M-H) plots reveal the soft ferrimagnetic behavior of the films. The post-deposition annealing of the film leads to increase in crystallite size with more uniform film surface and dense columnar growth compared to the as-deposited film. The increase in magnetization and decreases in Hr-values compared to that of as-deposited film are observed for annealed film. The optical band gap of the film is also found to increase with annealing.

Highly Stable In-Plane Microwave Magnetism in Flexible Li0.35Zn0.3Fe2.35O4(111) Epitaxial Thin Films for Wearable Devices.

With the advances in artificial intelligence and communication technologies, flexible microwave magnetic materials have become essential for flexible microwave detectors, wearable microwave sensors, and flexible spintronics. Here, a highly stable in-plane (IP) ferromagnetic resonance (FMR) and a tunable out-of-plane (OOP) FMR character are demonstrated in the flexible microwave magnetic Li0.35Zn0.3Fe2.35O4 (LZFO) (111) epitaxial thin films under external mechanical bending. Both the IP FMR line width and resonance field ( Hr) are basically unchanged when the sample was bent under an external tensile or compressive bending strain and deformation. However, the OOP FMR spectra (including Hr and absorption peak) could be tuned by mechanical bending, i.e., the LZFO sample possesses two OOP FMR absorption peaks at an external bending curvature. Meanwhile, excellent mechanical antifatigue and mechanical retention characteristics have also been obtained in the LZFO sample. The highly stable IP and the tunable OOP FMR spectra in the same LZFO sample with excellent mechanical antifatigue character have a promising prospect in microwave magnetic devices and flexible spintronics.