Saturation Remanent Magnetization Research Articles

Enhancing and modifying the optical, magnetic, and electrical features of PVA&PVP; composite filled with ZnFe2O4 nanoparticles for magneto-optical applications

Abstract This research employed a sol-gel method to synthesize zinc ferrite nanoparticles (ZnFe2O4 NPs). These nanoparticles were then dispersed within a blend of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) (with a weight ratio of 50:50) to fabricate polymer nanocomposite samples (PNCSs) via a solution casting technique. The XRD patterns suggest significant structural alterations in the nanocomposite compared to the pure polymer blend, which is evident in changes in crystallinity and cluster size (D). At the same time, the atomic arrangement within the material remains unaffected (d spacing). The FTIR absorption spectra were analyzed to assess the miscibility of PVA and PVP, as well as their interactions with the ZnFe2O4 NPs. The presence of characteristic peaks for both polymers without significant shifting suggested good miscibility. The optical bandgap of the nanocomposite samples decreases from 4.79 to 3.16 eV, and the absorption edge gradually shifts toward longer wavelengths with the addition of ZnFe2O4 NPs. Thermal analysis using TGA was also conducted to investigate how the samples decompose with increasing temperature. Coats-Redfern and Broido models were also used to study the activation energy. The magnetic properties of the PVA/PVP-ZnFe₂O₄ nanocomposites were assessed using the VSM technique at room temperature, revealing ferromagnetic behavior with a significant increase in saturation magnetization (Ms), remanent magnetization (Mr), and loop area (La) as the ZnFe₂O₄ content increased. Across the frequency range of 0.1 Hz to 10 MHz, the PVA/PVP-ZnFe2O4 NP samples exhibited significantly improved electrical conductivity and dielectric properties. In addition, the dielectric properties and electric modulus of these PNCSs were studied, where the ZnFe2O4 NPs successfully improved the host matrix's capacity for storing energy. As a result, these interesting physicochemical characteristics show how well these PNCSs are suited for use in flexible-type micro- and optoelectronic methods, such as nanodielectric substrates, bandgap regulators, photosensors, and UV shielders.

Investigation of structural, magnetic and morphological properties of Zinc and Cobalt-doped Nickel Ferrites

Abstract Nickel Ferrite nanocrystalline material doped with transition metal ions (Zn2+, Co2+) was obtained by chemical combustion method using respective nitrate hexahydrates and glycine as fuel. The phase purity of the prepared ceramic samples was ascertained using Powder X-ray diffraction (XRD) exhibiting an inverse cubic spinel structure with space group Fd 3 ‾ $\overline{\mathrm{3}}$ m. Lattice parameters follow the Vegard law, indicating a consistent lattice expansion. The formation of porous nanocrystalline ferrite was confirmed by Scanning Electron Microscopy (SEM) images and corroborated by Williamson-Hall analysis. Raman Spectroscopic analysis identified characteristic bands corresponding to vibrational modes of nickel ferrite (NiFe2O4) and revealed shifts in the peak position with doping by zinc (Zn) and cobalt (Co). Vibrating Sample magnetometry (VSM) analysis indicated varied magnetic behaviour with different dopants and concentrations highlighting the influence of cation substitution on magnetic properties. The specific saturation magnetization (M s ), remanent magnetization (M r ) and coercivity (H c ) are improved by the substitution of Zn2+ and Co2+ ions. This simple and cost-effective preparation technique holds promise for synthesizing high-quality nickel ferrite, which could find applications in magnetic and electronic devices.

Investigation on the structure formation, morphology, electronic and magnetic properties of BaFe12O19 nanopowders synthesized by utilizing sol-gel technique using L-sorbose as a fuel agent

Hexagonal barium ferrite (BaFe12O19) is a highly magnetic material due to its high resistivity, large permeability and low loss behaviour. It was mainly focused on applications in the electric, magnetic and telecom industries because of their good dielectric properties at microwave frequencies. The brown colored nanoparticles (NPs) of BaFe12O19 were carried out by the sol-gel approach using L-sorbose as a fuel synthesized from the ethylene glycol and oxalic acids. The synthesized nanopowders were characterized by thermal, X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR, photoluminescence (PL), ultraviolet visible (UV–Vis), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV) and vibrating sample magnetometer (VSM) techniques. XRD peak indicates the formation of good quality nanocrystalline hexagonal BaFe12O19 phase of the synthesized sample. The FT-IR spectra exhibited the significant vibrational frequencies of BaFe12O19 NPs were detected at 448, 578 and 768 cm−1 for 800 °C, which suggests the formation of a hexagonal phase. The SEM images of BaFe12O19 powders at 800 °C indicated the micro-sized flakes shape with crystallite size ranging from 40 to 65 nm. The EDS was performed to analyze the total energy distributions and elemental individual content of the prepared powders and it was also found that the content of Ba reduced as the content of Fe increased. Further, the physical properties of the synthesized NPs were determined by VSM analyzer and the high saturation magnetization (Ms = 18.41 emu/g), remanence magnetization (Mr = 10.20 emu/g) and magnetization coercive force (Hc = 5707 Oe). Overall, these results suggested the prepared nanoparticles calcined at 800 °C have the good potential for utilization in many applications such as magnetic recording, fast random access memory, electronic devices, etc.

Enhanced magnetic, ferroelectric, and photocatalytic properties of Nd and Co doped bismuth ferrite (Bi1−xNdxFe1−yCoyO3) ceramics

This study investigates the structural, magnetic, ferroelectric, and photocatalytic properties of bismuth ferrite ceramics co-doped with Nd and Co. The ceramics were synthesized using a combination of solid-state and mechanical milling techniques, and their compositions were varied within the range of Bi1−xNdxFe1−yCoyO3, with x and y ranging from 0.05 to 0.20. The materials were characterized using XRD (Rietveld refinement), WDXRF, Raman spectroscopy, and impedance analysis. Magnetic measurements revealed that the saturation magnetization (Ms) and remanent magnetization (Mr) significantly increased as the concentrations of Nd and Co increased. The magnetic properties showed an improvement, with the Ms value increasing from 8.12 emu/g for x = y = 0.05 to 18.67 emu/g for x = y = 0.20. Similarly, the magnetic response increased from 1.49 emu/g to 5.63 emu/g. The ferroelectric properties also exhibited improvement, with polarization values increasing from 0.79 µC/cm2 to 2.02 µC/cm2 at a frequency of 50 Hz. Photocatalytic activity was evaluated by measuring the degradation of organic dyes under visible light exposure, which showed a notable increase of up to 70 % when the doping concentrations were at their highest. These results suggest that Bi1−xNdxFe1−yCoyO3 ceramics have a wide range of applications, making them promising materials for advanced devices and environmental cleanup. By doping with Nd and Co, the materials’ properties are enhanced, leading to significant improvements in their ability to convert light into energy.

Influence of CoFe2O4 content on the multifunctional properties of BiFeO3–CoFe2O4 core-shell nanocomposites

The utilization of magnetoelectric composites, particularly core-shell configurations, enhances their versatile applications in various sectors such as medicine and data storage. Among these composites, the perovskite-spinel combination is distinguished by its significant potential. A series of (1-x) BiFeO3-(x) CoFe2O4 (where x = 0.0, 0.2, 0.5, and 1.0) nano core-shell structures were synthesized using a sol-gel auto-combustion method to explore their multifunctional capabilities. Structural analyses identified peaks corresponding to both perovskite and spinel phases. Field Emission Scanning Electron Microscopy revealed a reduction in average particle size with an increase in CoFe2O4 content.The particle size in the BFO80-CFO20 sample has been reduced from 243 nm to 34 nm. Additionally, Transmission Electron Microscopy images of the BFO80-CFO20 sample highlighted the evolution of core-shell structures. Our findings indicate that higher CFO concentrations significantly affect the dielectric, ferroelectric, and optical properties. The bandgaps of the nanocomposites BFO80-CFO20 and BFO50-CFO50 were estimated to be 1.43 eV and 1.39 eV, respectively. Magnetic analysis showed increases in both saturation magnetization and remanent magnetization with increased CFO content, while the coercive field followed a different trend. The saturation magnetization values for the samples BFO, BFO80-CFO20, BFO50-CFO50, and CFO were calculated as 0.205, 14.612, 28.374, and 74.105 (emugr), respectively. The measured values for the same samples were 0.08, 5.07, 11.34, and 34.01 (emugr), respectively. Further, the electrochemical properties were thoroughly investigated using cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy.

Controllable synthesis and magnetization of Fe3O4 microspheres wrapped with amorphous carbon

A straightforward solvothermal methodology was employed to synthesize [Formula: see text] microspheres and [Formula: see text]@C hybrids, where amorphous carbon encapsulated [Formula: see text] microspheres. This encapsulation was achieved by meticulously controlling the reaction duration and glucose concentrations within the hydrothermal process. Analysis via X-ray diffraction and Raman spectroscopy confirmed that all specimens retained a homogeneous [Formula: see text] phase. Following encapsulation, the [Formula: see text] particles were uniformly distributed across the amorphous carbon spheres, with fine particle sizes in the hybrids measuring less than 20 nm. Magnetic characterization revealed that parameters such as saturation magnetization, remanent magnetization, and coercivity of the [Formula: see text] microspheres could be significantly adjusted by varying the hydrothermal reaction time. Notably, the hybrids exhibited a 5- to 10-fold increase in both coercivity and remanent magnetization when compared to the pristine [Formula: see text] microspheres. Nonetheless, the saturation magnetization of the hybrids reached up to 90% of that observed in bulk [Formula: see text]. These magnetic properties are predominantly influenced by the size effect associated with the nanostructured [Formula: see text].

Exploring the supercapacitive potential of Sm3+ doped CoFe2O4 nanoparticles: Enhanced magnetic and dielectric properties

This study investigates the impact of Sm3+ substitution on the structural, electrical, magnetic, and electrochemical properties of CoFe2O4 nanoparticles prepared via a combined solid-state reaction and mechanical milling approach. Rietveld refinement analysis confirms the presence of single-phase cubic spinel structures within the Fd3m space group for both CoFe2O4 (CF) and Co0.95Sm0.05Fe2O4 (SmCF). Field emission scanning electron microscopy and energy dispersive spectroscopy are employed to validate the microstructure and elemental composition. Tauc plot analysis reveals a decrease in the band gap from 2.24 eV for CF to 2.07 eV for SmCF. Hysteresis loop measurements demonstrate an enhancement in saturation magnetization, remanent magnetization, and magnetic moment for SmCF, indicating improved magnetic properties. Furthermore, a substantial increase in magneto-crystalline anisotropy is observed with Sm³⁺ doping. Frequency-dependent dielectric properties are investigated using Havriliak–Negami fitting, confirming the presence of Cole-Cole dispersion. A direct correlation between the dielectric constant and temperature is identified, suggesting higher temperatures lead to elevated values. Notably, the incorporation of Sm³⁺ results in a significant enhancement in specific capacitance, positioning SmCF as a promising candidate for energy storage applications, particularly in supercapacitors.

Magnetic properties and coupled spin‒phonon behavior of M‒type Sr1-xSmxFe12O19 (0 ≤ x ≤ 0.15) nanoparticles

We thoroughly investigated the effects of Sm³⁺ doping on the magnetic, structural, hyperfine, and vibrational properties of Sr1-xSmxFe12O19 (0 ≤ x ≤ 0.15) nanoparticles, which were synthesized using the proteic sol-gel process. The Rietveld refined XRD patterns confirmed the presence of M-type SrFe12O19, alongside a minor fraction of α-Fe2O3. As Sm³⁺ doping increased, the unit cell volume fluctuated, decreasing from 691.73 ų at x = 0 to 690.67 ų at x = 0.10 and slightly rising thereafter. The incorporation of Sm³⁺ induced a conversion of Fe3+ to Fe2+, affecting lattice parameters and crystallinity. At x = 0.10, maximum crystallite size (56.48 nm) and X-ray density (4.83 g/cm³) were attained, alongside decreased microstrain, indicating improved crystallinity and reduced defects. However, at x = 0.15, an increase in microstrain suggested lattice instability. FTIR confirmed that bands in the range 400–600 cm⁻1 might be due to the stretching vibration of oxygen and metal (Fe–O) ions, confirming the formation of hexaferrite. Temperature-dependent Raman spectroscopy studies confirmed the presence of spin-phonon coupling in all samples in the ferrimagnetic transition at ∼725-735 K. Mössbauer spectroscopy elucidated that the substitution of Sr2+ by Sm3+ induced the most pronounced effect on the 12k, 4f2, and 2a sites, corroborating the evolution of the lattice constants and the fact that these three sites have Sr sites in their close vicinity. The room-temperature hysteresis loops exhibited narrow features, indicative of soft magnetic behavior. Saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) varied with Sm3+ doping content (x). Ms initially decreased from 62.62 emu/g and 22.03 emu/g at x = 0.00 to 54.96 emu/g and 19.63 emu/g at x = 0.10, respectively, and then increase to 59.77 emu/g and 21.86 emu/g at x = 0.15. Conversely, Mr and Hc showed a non-monotonic trend with x, suggesting complex interactions between dopant concentration and magnetic properties.

Improvement in the dielectric, magnetic, ferroelectric, and magnetoelectric coupling attributes of BaTiO3/CoNb0.02Fe1.98O4 composite systems

The search for new materials and compositions, in which the phenomena of ferrimagnetism and ferroelectricity are closely coupled, is of great technological interest. In the present study, composite systems of (BaTiO3)(100-x)%/(CoNb0·02Fe1·98O4)x% where x = 0, 2, 5, 10, 20, and 100% were produced. Initially, BaTiO3 (BTO) was made by sol-gel combustion approach and CoFe1·98Nb0·02O4 (CoFeNbO) was made by hydrothermal method. Both compounds were then combined via solid-state reaction route to form the composite systems. According to X-ray diffraction, the pristine BTO and CoNbFeO display tetragonal and cubic structures, respectively, and all composite systems consisted of the cubic phase for BTO and spinel phase for CoNbFeO. Scanning electron microscopy showed a decrease in grain size (from 0.552 μm to 0.194 μm) and porosity (from 18.65% to 4.57%) as the CoNbFeO content increases from x = 0 to x = 20%, respectively. The influence of magnetic CoNbFeO content on the magnetic, ferroelectric, magnetoelectric coefficient, electric, and dielectric properties of composite systems has been investigated. The ferromagnetic and ferroelectric natures of diverse composite systems are reflected via the registered M-H and P-E loops at ambient temperature. A steady increase in magnetic parameters such as saturation magnetization and remanent magnetization is observed as the spinel ferrite CoNbFeO content increases. Similarly, the values of the electric coercivity increased from 1.65 kV/cm for x = 0% to 3.99 kV/cm for x = 20%. The frequency-dependent dielectric and electrical measurements were also investigated at various temperatures. By raising the measurement temperature, the dielectric polarization was found to increase for composite systems with x > 2%. Interestingly, the tangent loss was reduced for different composite systems in comparison to pristine BTO and CoNbFeO materials. The lowest tangent loss values were noticed for x = 5% composite system. All composite systems revealed good magnetoelectric coupling with coupling coefficient magnitudes up to a maximum value of ∼22.5 mV/cm.Oe, indicating that they can be potential candidates for use in advanced multifunctional electric devices.

Study the Structural, Morphological and Magnetic Properties of (Bi Ni Fe2 O4/C) Nano Composite

In this work, bismuth nickel ferrite (Bix Ni1-x Fe2O4) supported by activated carbon (AC) with x=0, 0.3 and 0.5 were made and studied using the sol-gel method, and the samples were calcinated at 350 and 650 °C for 3 hours. XRD, FTIR, FESEM, and EDX spectroscopy were used to examine the chemical structure and morphology of bismuth nickel ferrite on activated carbon (Bix Ni1-x Fe2O4/ C). The XRD patterns show that when the temperature of the synthesized material is raised, the intensity and spread of the peaks decrease. This leads to more crystallization. FTIR studies were done in the frequency range (400–4000) cm-1, and the FTIR spectrum of (Bix Ni1-x Fe2O4/ C) shows the two significant absorption bands near the frequency ranges 500 cm-1 and 700 cm-1. FESEM with particles that were between 17 and 60 nm in size was used to study the surface morphology. The EDS plots revealed the existence of no extra peaks other than constituents of the taken up composition. The decrease in saturation magnetization (Ms) and remanence magnetization (Mr) is seen through the utilization of a vibrating sample magnetometer (VSM).

Structural, magnetic, impedance and electric modulus response and dielectric relaxation in Co-doped inverse spinel [formula omitted] nanoferrite

In this research work, we report synthesis, structural, electric and magnetic properties of Cu1−XCoXFe2O4(x = 0.05, 0.10, 0.15, 0.20) nanoferrite. All the samples are synthesized using sol-gel auto-combustion method. X-ray diffraction patterns validate the formation of single phase tetragonal structure at room temperature for all the samples. Absence of secondary phases confirms the successful substitution of Cu2+ by Co2+ ions in CuFe2O4 matrix. Dielectric analysis reveals that all the materials exhibit remarkable single dielectric relaxation. The dielectric relaxation peaks are observed between 150–225 °C. In addition, Co-doped CuFe2O4 exhibit marked enhancement of dielectric constant value for potential technological applications. Further, the correlated barrier hopping (CBH) model well explains the conduction phenomena in all the samples. Activation energy values are analyzed by applying the Arrhenius equation. Impedance analysis indicates that both grain and grain boundary effects contributed the electrical response in the ferrites which is confirmed from the plot of Z″ vs. Z′. The bulk and grain boundary response are further determined by modeling the impedance data with an equivalent circuit. Modulus study confirms the existence of non-Debye type of relaxation in the synthesized ferrites. Magnetic study shows the improved value of magnetic parameters such as saturation magnetization (Ms), remanent magnetization (Mr) and coercive field (Hc).

Influence of annealing temperature on microstructure, magnetic and electrical properties of Ce doped cobalt ferrite nanoparticles

Cerium doped cobalt ferrite nanoparticles with chemical formula CoFe1·9Ce0·1O4 were synthesized at different annealing temperatures (600, 700, 800, 900 and 1000C°) via sol-gel auto-combustion method. Thermal analysis for sample annealed at 1000C° was examined through differential scanning calorimetry (DSC) and revealed the presence of exothermic peak at around 500C° attributed to crystallization of prepared nanoferrites. Structural analysis such as phase formation, crystallinity and morphology was investigated by x-ray powder diffraction (XRD) and high resolution transmission electron microscope (HRTEM). XRD study revealed higher dependence of grain size growth with annealing temperatures as compared to lattice parameter. HRTEM investigation confirmed that grains have almost uniform morphology with some agglomeration and confirmed values of lattice parameters and grain sizes calculated from XRD data. Magnetic hysteresis was studied by vibrating sample magnetometer (VSM) at room temperature with an applied field of 20 kOe. The results showed an increase in saturation magnetization and remanent magnetization with increasing of annealing temperature, whereas a decline in coercivity was observed. Distribution of cations at tetrahedral and octahedral sites was investigated using x-ray and magnetic parameters which confirmed the mixed spinel ferrite nature of samples. Dielectric properties were carried out at room temperature in the range 0.1Hz–3.0 MHz. Both dielectric constant and ac conductivity decreased with rising of annealing temperature. Variation of dielectric loss tangent, impedance, electric modulus and relaxation time with temperature were also investigated. The effect of annealing temperature on the structure and its impact on magnetic and dielectric properties has been examined and discussed.

Physical characterization, magnetic interactions and DC electrical resistivity properties of La3+ substituted NiZnCd nano ferrites

In this article, we substituted La3+ ions to explore the structural, magnetic, and DC electrical resistivity properties of Ni0.5Zn0.4Cd0.1Fe2-xLaxO4 (x = 0.0, 0.02, 0.04, 0.06, and 0.08) nano-structured spinel ferrites. We employed X-ray diffraction (XRD), Field-emission scanning electron microscopy (FESEM) with Energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometry (VSM), and electrical measurements to characterize the studied samples, which were synthesized using the sol–gel auto-combustion process. XRD analysis confirmed that the prepared materials formed a single-phase nanostructure. Using Debye-Scherer's formula, we calculated the average crystallite size, which ranged from 29.01 to 21.52 nm. FESEM images demonstrated that each sample exhibited spherical nanocrystalline behavior. The variations of the prepared samples were confirmed constitutionally by EDX. The FTIR data revealed two absorption bands for all synthesized materials at υ1 = 562.18 to 590.51 cm−1 and υ2 = 410.18 to 430.51 cm−1, corresponding to the tetrahedral and octahedral sites of the spinel structure, respectively. Vibrant sample magnetometry spectra were utilized to investigate how La3+-doping affects the magnetic characteristics of NiZnCd ferrite. Due to enhanced La3+-doping, saturation magnetization, and coercivity values decreased. The La3+ doping of NiZnCd nano ferrites resulted in changes in saturation magnetization (from 83.66 to 69.57 emu/g), coercivity (from 33.75 to 60.51 Oe), and remanence magnetization (from 29.62 to 33.12 emu/g). These variations suggest the potential utility of the samples for magnetic recording and memory applications. The semiconducting behavior has been confirmed by the DC electrical resistivity measured values using a two-probe method. Data on DC electrical resistivity were also utilized to determine carrier concentration and activation energy, establishing a connection with La3+ replacement.

Effect of particle size and composition on local magnetic hyperthermia of chitosan-Mg1-xCoxFe2O4 nanohybrid.

In this study, Mg1-xCoxFe2O4 (0≤x ≤ 1 with ∆x = 0.1) or MCFO nanoparticles were synthesized using a chemical co-precipitation method and annealed at 200, 400, 600, and 800°C respectively to investigate the structural properties of the materials by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Controlled annealing increased particle size for each value of x. The aim was to investigate how specific loss power (SLP) and maximum temperature (Tmax) during local magnetic hyperthermia were affected by structural alterations associated with particle size and composition. The lattice parameter, X-ray density, ionic radius, hopping length, bond length, cation-cation distance, and cation-anion distance increase with an increase in Co2+ content. Raman and FTIR spectroscopy reveal changes in cation distribution with Co2+ content and particle size. Magnetic properties measured by the physical property measurement system (PPMS) showed saturation magnetization (Ms), coercivity (Hc), remanent magnetization (Mr/Ms), and anisotropy constant (K1) of the Mg1-xCoxFe2O4 nanoparticles increase with Co2+ content and particle size. When exposed to an rf magnetic field, the nanohybrids experienced an increase in both the SLP (specific loss power) and Tmax (maximum temperature) as the particle size initially increased. However, these values reached their peak at critical particle size and subsequently decreased. This occurs since a modest increase in anisotropy, resulting from the presence of Co2+ and larger particle size, facilitates Néel and Brownian relaxation. However, for high anisotropy values and particle size, the Néel and Brownian relaxations are hindered, leading to the emergence of a critical size. The critical size increases as the Co2+ content decreases, but it decreases as the Co2+ content increases, a consequence of higher anisotropy with the increase in Co2+. Additionally, it is noteworthy that the maximum temperature (Tmax) rises as the concentration of nanohybrids grows, but the specific loss power (SLP) decreases. An increased concentration of chitosan-MCFO nanohybrids inhibits both the Néel and Brownian relaxation processes, reducing specific loss power.

Flexible and twistable free-standing PDMS-magnetic-nanoparticle-based soft magnetic films with robust magnetic properties

In this paper, we develop multifunctional, physically soft, mechanically compliant, and magnetically responsive PDMS films, with embedded Fe3O4 nanoparticles, that show robust magnetic properties over a significant range of mechanical deformation. First, we establish that the magnetic properties, namely the saturation magnetization (M s), remanent magnetization (M r), and intrinsic coercivity (H ci) of these PDMS films in highly deformed configurations, i.e. in folded, twisted (with different twist angles), and bent (flexed) configurations, show very little degradation compared to those obtained in undeformed configurations. Next, the films were subjected to repetitive cycles of zero-to-max deformation (R = 0) and the saturation magnetization of the films was shown to not exhibit any significant degree of progressive degradation as a function of cyclic deformation history. These findings confirm the excellent robustness and cyclic durability of magnetic properties shown by these magnetic and compliant PDMS films and point to their suitability for wearable electronics applications.

Enhanced Magnetic Properties of Gd-Doped ZnO by Varying the Gd Concentration via Co-Sputtering Technique

This study reports on the effect of Gd concentrations on the properties of Gd-doped ZnO films. The films were prepared using co-sputtering method at room temperature. Characterization tools such as X-ray diffraction (XRD), atomic force microscopy (AFM), and vibrating sample magnetometer (VSM) were used to analyze the properties of the prepared films. XRD results observed that all the films are well crystalline and designated to the hexagonal wurtzite structure of ZnO with no secondary phases, which confirmed the successful of doping the Gd into ZnO. Topography analysis from AFM discovered the increase of Gd concentrations of Gd-doped ZnO films leads to the increase in grain size and rougher surface of the films. The magnetization of the films effectively depends on the Gd concentrations, which the diamagnetic behavior changed to ferromagnetic behavior upon Gd doping. A film with higher Gd doping concentration is more effective than lower Gd doping in terms of saturation magnetization (Ms), coercivity (Hc) and remanent magnetization (Mr). These findings revealed that optimizing the Gd concentration is very crucial in enhancing the magnetic properties of Gd-doped ZnO films.

Room‐Temperature Macroscopic Ferromagnetism in Multilayered Graphene Oxide

AbstractGraphene has a long spin lifetime and hyperfine interactions, favoring its potential application as spintronics. Despite the recent discoveries of spin‐containing graphene materials, graphene‐based materials with room‐temperature macroscopic ferromagnetism are extremely rare. In this article, room‐temperature ferromagnetic amorphous graphene oxide (GO) is synthesized by introducing abundant oxygen‐containing functional groups and C defects into single‐layered graphene, followed by a self‐assembly process under supercritical CO2 (SC CO2). Such amorphous GO exhibits the highest saturation magnetization (1.71 emu g−1) and remanent magnetization (0.251 emu g−1) compared to the rest of metal‐free graphene‐based materials at room temperature. Experimental and theoretical investigations attribute such strong ferromagnetism to the bridging of the adjacent graphene layers though the out‐of‐plane oxygen‐containing groups, which leads to asymmetric lattices with large net magnetic moments.

Effects of SmCo Co-substitution on the magnetic and electrical properties of low temperature sintering synthesized strontium hexaferrite

In order to mitigate the rapid grain growth, a sintered ferrite magnet exhibiting stable characteristics was successfully synthesized. M-type strontium ferrite Sr1-xSmxFe12-xCoxO19 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.10) was synthesized via a low-temperature co-firing method, incorporating an appropriate quantity of Bi2O3 and CuO as additives within the solid-phase reaction process. The magnetic and electrical properties of the resulting composites were meticulously examined, and X-ray diffraction (XRD) analysis was performed for structural characterization. The findings reveal that a pure hexagonal strontium phase is achieved consistently when the substitution level, x, remains below 0.5. With an increase in the substitution level, a heterogeneous phase α-Fe2O3 becomes apparent within the phase structure. Upon introducing doping elements, the subtle incorporation of SmCo (x ≤ 0.02) enhances the saturation magnetization, remanent magnetization, and coercivity of the composite material. Moreover, the resistances of grain and grain boundary (Rg, Rgb) have been downscaled from 1.856 × 106Ω and 3.61 × 106Ω to 3.182 × 104Ω and 4.37 × 105Ω respectively. Consequently, the Sr1-xSmxFe12-xCoxO19 ferrite sintered under low-temperature conditions demonstrates outstanding electromagnetic characteristics, presenting a viable option for materials in microwave device applications.

Magnetic properties and electron oxidation state transition of immunomagnetic nanoparticles specifically captured with the target bacteria

Immunomagnetic nanoparticles (IMNPs) have been widely applied for the capture and concentration in the rapid detection of target bacteria. In this research, the focus was on studying the changes in magnetic properties changes of the IMNPs when they were attached to bacterial cells. These alterations in properties could facilitate an even rapid detection of the target bacteria and eliminate the need for culturing on plating media. The variation of magnetizing values, including saturated magnetization (Ms), remanent magnetization (Mr), coercivity force (Hc), and magnetic susceptibility (χm), was analysed through M-H loops. It was observed that the magnetizing properties of the IMNPs underwent changes based on the concentrations of Salmonella Typhimurium cells in the test solution. The correlation of this phenomenon was confirmed by the results of synchrotron x-ray absorption spectroscopy (XAS), which revealed electronic transition changes in the IMNPs after capturing the bacteria cells. Additionally, the electronic bands of the magnetite nanoparticle [Fe(II) and Fe(III)] were detected, indicating an electronic transformation between the Salmonella cells and the bound IMNPs. The XAS change was further verified using different cell types, such as Campylobacter jejuni which also showed electronic transformation after attaching to IMNPs. These findings suggest that IMNP-cell attachment triggered the change in the magnetic properties of IMNPs. Such insights could serve as valuable information for the development of novel rapid bacteria detection assays/devices using magnetic sensing techniques.

Efficient energy and memory storage capabilities in optimized BiFeO3/MnMoO4/NiFe2O4 triphasic composites for futuristic multistate devices.

The emergence of multiferroic materials particularly bismuth iron oxide (BiFeO3) with distinctive magnetoelectric, and high energy storage capabilities, present pivotal aspects for next-generation memory storage devices. However, intrinsically weak magnetoelectric coupling limits their widespread applications, that can be leap over by the integration of BiFeO3 with enriched ferroelectric, and ferro/ferrimagnetic materials. Here, a series (1 - x)[0.7BiFeO3 + 0.3MnMoO4] + xNiFe2O4 (x = 0.00, 0.03, 0.06, and 0.09) is synthesized via citrate-gel based self-ignition, and solid-state reaction routes. Phase purity and crystallinity of tri-phase composites with surfaces revealing random and arbitrarily shaped grains are assured by X-ray diffraction, and field emission scanning electron microscopy, respectively. Dielectric studies illustrated non-linear trend for broad range of frequencies as predicted by Maxwell-Wagner theory along with single semicircle arcs in Nyquist plots that exposes grain boundaries effect. An enriched 68.42% of ferroelectric efficiency is featured for x = 0.06 substitutional contents, while magnetic computations demonstrated improved saturation magnetization (M s), remanence magnetization (M r), and coercive applied magnetic field (H c) values as 5.87 emu g-1, 0.96 emu g-1, and 215.19 Oe, respectively for x = 0.09 phase-fraction. The intriguing linear trends of magnetoelectric coupling for all the compositions are corroborating them propitious contenders for futuristic multistate devices.