Saturation Magnetization Ms Research Articles

Improved magnetic properties of Fe substituted La2CoMnO6 for spintronic applications

A detailed study of magnetic behaviour of double perovskites was carried out by developing La2Co1-xFexMnO6; (x = 0.0, 0.2, 0.5, 0.8 and 1.0) via sol–gel technique. All samples showed single magnetic transition except pure LCMO (x = 0.0) and LCFMO2 (x = 0.5). Temperature dependent inverse magnetic susceptibility (χ-1) was fitted in accordance with Curie-Weiss law. μeff (effective magnetic moment) was determined for all the developed samples. Pure LCMO showed a downward divergence from Curie-Weiss law below 230 K but above transition temperature which indicates the characteristics of Griffiths phase. Saturation magnetization (Ms) increased initially and then decreased, whereas coercive field (Hc) was found to be monotonous decreased with increase in Fe content. LCFMO1 (x = 0.2) was noticed to have maximum Ms (38.87 emu/g) which indicated that the magnetic properties of pure LCMO were improved with Fe substitution, but for lower substitution only. Magnetization vs. field (M−H) curves were not well saturated even at a magnetic field of 60 kOe, therefore, values of Ms for all the samples were estimated using law of approach to saturation. With increase in Fe content, an increased anti-site disorder among Mn and Co strengthened antiferromagnetic (AFM) super exchange interactions and weakened ferromagnetism (FM). Therefore, substitution of Fe on Co-site was responsible for systematic decrease in saturation magnetization when × exceeded 0.2.

Nanocomposites Based on Polyethylene and Nickel Ferrite: Preparation, Characterization, and Properties.

Composite materials based on NiFe2O4 nanoparticles and polyethylene matrix have been synthesized by thermal decomposition to expand the application area of high-pressure polyethylene by filling it with nanoscale particles. The synthesized compositions were obtained in the form of a dark gray powder and compressed for further study According to TEM, the average particle size in composites was 2, 3, and 4 nm in samples with a filling of 10%, 20% and 30%. The concentration dependences of the specific electrical resistivity ρV, dielectric permittivity ε, saturation magnetization MS and the parameters of reflection and attenuation of microwave power of the obtained composites were investigated. The threshold for percolation in such materials is found to be within a concentration range of 20…30%. The electronic and atomic structure of composites was studied by methods of Mössbauer spectroscopy, X-ray diffraction and X-ray absorption spectroscopy. The closest atomic environment of nickel and iron in nanoparticles is close to that of crystalline NiFe2O4. The dependence of the nanoparticles size as well as the dependence of the number of tetrahedral or octahedral iron positions in nickel ferrite nanoparticles to their content in polyethylene matrix is established. It is shown that composite materials based on NiFe2O4 nanoparticles and polyethylene matrix can be used as components of electromagnetic compatibility systems.

Enhanced photodegradation of CuCo2O4 nanoflower for the dye degradation of Rhodamine B and Methyl Violet

The investigation examined into the effect of different hydrothermal reaction temperatures and durations on the formation of nanoflower-shaped CuCo2O4 nanostructures (CCO NPs). The structural, morphological, functional, optical, and magnetic properties of the synthesized CCO NPs were thoroughly examined. The optimal calcination temperature was determined using Thermogravimetric and Differential Thermal Analysis (TG/DTA), which identified 400 °C as the ideal temperature. Following X-ray Diffraction (XRD) analysis, pure CuCo2O4 samples were formed, with calculated average crystallite sizes of 27 nm for CCO-A, 48 nm for CCO-B, 30 nm for CCO-C, and 31 nm for CCO-D samples. Fourier Transform Infrared (FTIR) analysis provided additional confirmation of pure CuCo2O4 formation, with characteristic bands in the 665–662 cm-1 and 583–567 cm-1 ranges indicating the presence of CuO and CoO bonds. SEM, High-Resolution SEM (HRSEM) and High-Resolution Transmission Electron Microscopy (HRTEM) all supported the observation of a distinct flower-like structural morphology. The optical properties of an optimized sample were revealed by UV–Visible Diffuse Reflectance Spectroscopy (UV-DRS) analysis, which revealed a band gap of 3.3 eV. According to Vibrating Sample Magnetometer (VSM) results, the magnetic behavior of CCO-D nanostructures at room temperature exhibited paramagnetic characteristics. The saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) values were determined to be 0.26218 emu/g, 2.7214 × 10–3 emu/g and 29.787 Oe, respectively. To evaluate photocatalytic performance, the CCO-D photocatalyst was used to degrade Methyl Violet and Rhodamine B dyes. CCO-D degraded MV dye with greater efficiency (93%) than RhB (85%) when exposed to sunlight. These findings highlight CCO-D's potential as a photocatalyst for the degradation of organic dyes.

“Structural and magnetic properties of ferric oxide nano-particles”

Magnetic Fe3O4 nanoparticles (NPs) were successfully synthesised via the co-precipitation method. The structural and magnetic properties of ferrite nanoparticles were studied using XRD, TEM, RAMAN, FTIR, and VSM. The Fe3O4 nanoparticle product is obtained as a black crystalline powder with an average particle size of 37.553 nm. The particle size was also confirmed by transmission electron microscopy (TEM). The XPS spectra analysis was found to be very useful for the detection of both + 2 and + 3 ions of iron in Fe3O4. The saturation magnetization (Ms) and coercivity come out to be 72 emu/gm and 13 oe respectively. FTIR determines the presence of various bonds that are Fe-O, COO-Fe, –CH 3, and –OH.

Microstructure, magnetic properties, and loss performance of the Cu-substituted MnZn ferrites

While the Cu substitution in NiCuZn ferrites is known to enhance densification and increase the initial permeability (μi), little is known about its effects in the MnZn based ferrites, which naturally possess a higher saturation magnetization (Ms) and μi. In this study, the effects of Cu substitution for Mn on the power MnZn ferrites (Mn0.71-xCuxZn0.22Fe2.07O4, x = 0.00–0.35) are investigated. With increasing Cu content, enhanced density, reduced porosity, and significant grain growth are observed. The cation distribution was determined using the Rietveld refinement, showing the strong tendency of Cu2+ ions to occupy the octahedral sites of the spinel lattice. The magnetization curves show reduced Ms with increasing Cu content. The magnetic anisotropy (|K|) was also determined from the magnetization curves using the law of approach to saturation and is seen to be increased by the increasing Cu content. The reduced Ms and increased |K| lead to the dramatic reduction of μi from 2503 (x = 0.00) to 151 (x = 0.35) at room temperature. Despite the reduced Ms at room temperature, the Curie temperature (TC) is seen to increase with increasing Cu content from x = 0.05 to x = 0.35, indicating the relocation of cations at an elevated temperature. The cut-off frequency (fr) is increased with increasing Cu content, which corresponds to the reduced μi. Moreover, the core loss (Pcv) of the MnCuZn ferrites was tested at 100kHz/200 mT, 200kHz/125 mT, and 300kHz/100 mT at room temperature, and is found to deteriorate with the increasing Cu content.

Exploration on the Structural, Optical, Morphological and Magnetic Properties of Hematite Nanoparticles and Their Antibacterial Activity

Hematite (α-Fe2O3) nanoparticles have been prepared by the conventional chemical precipitation synthesis technique. The prepared samples were subjected to structural, morphological, optical, magnetic and antibacterial behaviours. The diffraction analysis implies that the measured crystallite size of α- Fe2O3 nanoparticles is found to be 39 nm. The UV-visible absorption spectroscopy exhibits a strong absorption around 560 nm which is characteristics of Fe2O3 nanoparticles and the calculated bandgap value is found to be 2.07 eV. The presence of iron oxide polymorphs can be demonstrated by displaying phonon modes in Raman spectroscopy. Fourier-transform infrared spectroscopy (FTIR) study is used to identify the existence of functional groups and chemical structure of the synthesised Fe2O3 nanoparticles. Magnetic analysis displays hysteretic behaviour at room temperature with saturation magnetization Ms = 0.0036 emu/gm, the remanent magnetization Mr = 0.000698 emu/gm, and coercivity Hc = –0.27 Oe, respectively. The antibacterial activities of these α-Fe2O3 nanoparticles were investigated on pathogenic bacteria Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus aureus, and E. coli by a zone of inhibition method.

Ferroelectric, Magnetic and Dielectric Properties of SrCo0.2Zn0.2Fe11.6O18.8 Hexaferrite Obtained by “One-Pot” Green Sol-Gel Synthesis Utilizing Citrus reticulata Peel Extract

SrCo0.2Zn0.2Fe11.6O18.8 hexaferrite was obtained by a “one-pot” green sol-gel synthesis method utilizing aqueous mandarin orange (Citrus reticulata) peel extract as an eco-friendly reactant. The research objective was to analyze the influence of cobalt and zinc co-doping and the synthesis process on the structure, morphology, magnetic, dielectric and ferroelectric properties of strontium hexaferrite in view of future applications. Structural and morphological characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM-EDX) confirmed the formation of a Co and Zn ion incorporated M-type magnetoplumbite with c/a lattice parameter ratio of 3.919 as crystallite nanoplatelets of 32 and 53 nm in thickness and width, respectively. The magnetic hysteresis loop of the synthesized powder recorded by a vibrating sample magnetometer (VSM) at room temperature confirmed its ferromagnetic nature with a coercive field (Hc) of 2539 Oe and a saturation magnetization (Ms) and remanent magnetization (Mr) of 44.6 emu/g and 21.4 emu/g, respectively. Room temperature ferroelectric loops measured at 100 Hz showed a maximal (Pmax) and a remanent (Pr) polarization of 195.4 and 31.0 nC/cm2, respectively. Both increased when the magnitude of the applied electrical field increased in the 1–24 kV/cm range. The dielectric constant decreased with the frequency increase, in accordance with the Maxwell–Wagner model, while the conductivity changed according to the Jonscher power law. The complex impedance was modeled with an equivalent circuit, enabling identification of the dominant contribution of grain boundary resistance (272.3 MΩ) and capacitance (7.16 pF).

Effect of low sintering temperature on the structural and magnetic properties of M-type strontium hexaferrite

A pure M-type strontium hexaferrite with nominal composition SrFe12O19 has been prepared via the modified conventional citrate precursor method.The entirework emphasizes on improvingthe standardof hexagonal ferrite without undergoing high-temperature thermal treatments. By incorporating some adjustments in processing conditions, the prepared sampleis sintered at 800 °C and 910 °C, identified through thermalgravimetric analysis(TGA/DTA). The impact of the low-temperature sintering process on structural, spectroscopic, and magnetic properties are investigated via using different characterization techniques like XRD, FESEM, FTIR, Raman spectroscopy (RS), and VSM respectively. The XRD confirmed the formation of the M-phasealong withsome impurities of Fe2O3 and these results are strongly supported via both FTIR and RS. Similarly, FESEM analysis confirmed the formation of densely packed grains some hexagonal platelets. The magnetic properties of SrM hexaferrites show the increment of saturation magnetization Ms from 81 emu/g to 92 emu/g as the sintering temperature increases from 800 °C to 910 °C. Apart from the higher Ms for SrM hexaferrite, the Hc values 107 Oe and 262 Oe respectively are the vital findings of this research. This rare nature of SrM hexaferrite signifies the erection of soft character in hard SrM hexaferrites. Moreover the abrupt increase in the squarenes ratio (SQR) from 0.26 to 0.54 represents the transformation from multidomains to single domain. Material with such properties can be utilized in switching devices, recording media, high frequency applications.

Investigation of the effects of Cu layer thickness and annealing temperature under air atmosphere on the properties of Co/Cu multilayer films

In this study, the suitability of Co/Cu multilayer films with different physical conditions (varying thickness values and systematic annealing processes) in magnetic technology applications is discussed. Co/Cu films were deposited by the sputtering technique. The effects of different thicknesses of non-magnetic (Cu) layers and annealing temperature on magneto-structural properties were investigated. Different thicknesses of Cu layers were determined as 34 nm, 10 nm, 4 nm. Additionally, two annealed situations were considered to investigate the annealing effect. While the first one is exposing the films to 80 °C and 130 °C for 240 s, second one is annealing the films at 180 °C for different exposure times (50 s and 150 s). All films that have different thicknesses of Cu layers crystallized in (111) plane of the face centered cubic (fcc) structure. The intensity of this peak increased with increasing Cu layers thickness. Variation in the thickness of Cu layers has an important effect on the film surface. Saturation magnetization (Ms), coercivity (Hc) and squareness (Mr/Ms, Mr: remanent magnetization) were considerably affected by variation of the Cu content and film surface caused by the change in the thickness of the Cu layers. The film with 4 nm Cu layer thickness has the highest Ms, lowest Hc values and high Mr/Ms ratio. This indicates magnetically high efficient compared to the other films in the same series. The fcc structure continued to exist for the films annealed at 80 °C and 130 °C for 240 s. It was found that the annealing procedure transfigured the film surface and the differences in Ms and Hc values can be mostly attributed to this transfiguration because of the same film content revealed. An increase in Ms value, and a slight decrease in Hc and Mr/Ms values were detected for the annealed film at 130 °C, compared to the film annealed at 80 °C. It was also seen that the film structure was damaged at 180 °C because of excessive heat transfer.

Photocatalytic, electrical, and magnetic properties of carbon dots/hexaferrite's composites

The Y-type hexaferrite and its nanocomposite with carbon dots have been made by using a hydrothermal approach, whereas BaSrZn2-xMnxFe12-2ySiyNiyO22 (x = 0.0, 0.25, 0.5, 0.75, and 1.0) was made using a conventional microemulsion process. A variety of approaches are used to explore the structural features, surface area, and morphology of the materials. As indicated by on-site substitutions and super-exchange interaction, saturation magnetization (Ms) and magnetic remanence (Mr) rise from 18 to 6 to 47.4 emu g−1 and 6.7–18.3 emu g−1, respectively with x,y = 0.75, although coercivity (Hc) declines from 1.4 to 0.39 kOe. The ferrite material's electrical resistivity enhanced from 25.85 × 106 to 49.13 × 106 Ω-cm. The increased saturation magnetization (Ms), magnetic remanence (Mr), and electrical resistance of ferrite material make it suitable for both high-density recording and microwave devices. The photocatalyst (composite) for the degradation of Rhodamine B in the presence of visible light was made from SrBaZn1.25Mn0.75Fe10.5Si0.75Ni0.75O22/CDs with different ratios. Photocatalysts with a modest CDs concentration (2.5 wt%) successfully degraded Rhodamine B (RhB) up to 94%. After eight rounds, the composite showed excellent structural stability and good reusability. The trapping experiments confirmed that OH radical species are the major contributor in the degradation process. The composite material could be used to catch visible light and purify the environment from various pollutants in the future.

Impact of Sc3+/In3+ ions co-substitution on structural, magnetic, and microwave features of SrFe12O19 hexaferrites

ScIn→Sr NHFs have been synthesized via the sol-gel combustion method. The phase and morphonology were analyzed via XRD, SEM, TEM, and HR-TEM. XRD measurements confirmed the purity of all products having the crystallite size (DXRD) of 31–77 nm obtained via Rietveld refinement. The agglomeration of products was observed in SEM and HR-TEM images due to their magnetic character. SEM images revealed the hexagonal-shaped nanoparticles. Mössbauer spectra showed that In3+ and Sc3+ ions are located at generally octahedral (Oh) 4 f2 site. The electron density s of iron ions of 4 f2 and 2a sublattices is affected by doping content. The obtained M-H curves (field-dependence of magnetization) demonstrated ferrimagnetic hysteresis loops at both 300 and 10 K. The analysis of M-H curves also showed that the saturation magnetization (Ms) first declined until x = 0.03, then grew up to x = 0.05, and returned to decrease thereafter. The coercivity (Hc) decreased sharply with Sc-In substitution, transforming the magnetic character of samples from hard to soft. Microwave (MW) properties were measured and analyzed between 33 and 50 GHz. It was demonstrated that the increase of the Sc3+/In3+ concentration led to modifications in amplitude-frequency characteristics of the electromagnetic absorption process. It was shown that Sc3+/In3+ substituted Sr NHFs can be used for developing radioelectronic coatings and providing electromagnetic compatibility.

Multiferroic behavior of room temperature bismuth ferrite with tailored calcination temperature

One of the few materials that is multiferroic (antiferromagnetic and ferroelectric) is bismuth ferrite. In this study, we used the sol-gel method to create multiferroic bismuth ferrite and examined its structural and optical characteristics. The annealing temperature used to create bismuth ferrite was 600°C. The rhombohedral crystal structure was revealed by X-ray diffraction (XRD) investigation. The XRD diffractogram data examines the phase and planes of orientation for the synthesized materials. The crystalline size for the peak was determined using the Scherrer equation. Analysis using the Fourier transform infrared (FTIR) confirmed the existence of M-O octahedral and tetrahedral coordinates of the M-O bonds formed. The Fourier transform infrared in the wavenumber range of 500–850 cm−1 has been used to study the vibrational modes of the octahedral and tetrahedral metal complexes in the sample. Studies using a FESEM show that the synthesized nanocomposite has morphological characteristics, including interconnected agglomerates with spherical, irregular, or non-uniform elongated forms. By increasing the loading percentage of bismuth ferrite, the composite remnant magnetization (Mr) and saturation magnetization (Ms) values were discovered to be 0.43701 emu/g and 0.1940 emu/g, respectively. A frequency range of 10 Hz to 106 Hz was used to study the dielectric measurement of the nanocomposites. In the temperature range of 310 to 525 K, the AC conductivity has been measured, and it has been discovered that conductivity decreases as temperature rises. A temperature increase results in a reduction in the dielectric constant and dielectric loss. The initial data imply that the nanocomposite is a possible contender for use in capacitors with high dielectric constants. The composite will be useful for usage in hard disc components due to its magnetic characteristics, which is significant.

Multiferroic properties of BiFeO3 thin films with Ce substitution

In this study, we investigated the crystalline structure, ferroelectricity, leakage current density, magnetic, and nanomechanical properties of BiFeO3 (BFO) films with Ce substitution. Bi1-xCexFeO3 (BCFO) films with x = 0.00, 0.03, 0.06, 0.09, and 0.15 were deposited on glass substrates by using pulsed laser deposition. The experimental results showed that the BCFO films mainly composed the perovskite phase. The structure changed from rhombohedral when x = 0.00 to pseudo-cubic when x = 0.03, and pseudo-cubic phase coexisted with an additional Bi2Fe4O9 phase when x = 0.06–0.09. The BCFO films exhibited improved ferroelectricity and desirable magnetic characteristics. The remanent polarization (2Pr) increased significantly with the Ce concentration, reaching 189.3 μC/cm2 and 100.0 μC/cm2 when x = 0.03 and x = 0.06, respectively, but decreasing at higher Ce contents. The BCFO film with x = 0.03 had a remarkable 2Pr value of 189 μC/cm2 after 108 cycles due to the high (110) texture, fine microstructure, and flat interface resulting in strong anti-fatigue properties. The leakage mechanisms in the BCFO films were also examined. The films exhibited enhanced saturation magnetization (Ms) values ranging from 3.8 to 10.0 emu/cm3, which were attributed to suppression of the spiral spin configuration and the larger magnetic moment associated with the Ce3+ ion. The nanomechanical characteristics of the BCFO films, such as hardness, were significantly influenced by the grain size and phase composition. These findings provide valuable insights into enhancement of the multiferroic properties of BFO polycrystalline films through Ce substitution for use in various applications.

Structural, morphological, and magneto-dielectric features of Ni-Co-Pr ferrites for high density memory and high frequency devices

Praseodymium (Pr3+) substituted Nickel-Cobalt ferrites with composition Ni0.3Co0.7PrxFe2-xO4 and concentration (x = 0.00, 0.05, 0.10, 0.15, 0.20) were synthesized via sol–gel approach. The crystallite size was lying in 10.94–25.44 nm range having decreasing tendency and lattice constant was varying between 8.30 and 8.39 Å. Two absorption bands were seen in infrared spectroscopy around 550 cm−1 and 430 cm−1, representing spinel structure. Morphological analysis revealed particle size of ≈ 26.87 nm. Magnetic investigations disclosed decreasing trend in saturation magnetization (Ms), retentivity (Mr) and coercivity (Hc) and were determined in 19.77–50.75 emu/g, 0.77–19.48 emu/g, and 87.23–943.27 Oe range, respectively. Dielectric parameters showed decreasing trend with increase in frequency. Dielectric constant and loss were decreased from 3.64 to 2.59 and 0.502–0.420 for Pr3+ concentration × = 0.00–0.20 at 0.5 GHz, respectively. AC conductivity showed elevation with increasing applied frequency. These reported magneto-dielectric features suggest possible use of material in high density memory and high frequency devices.

Effect of magnetic field annealing on magnetic properties and corrosion resistance of MnBi alloy

Herein, MnBi alloys are prepared using melt spinning and magnetic-field annealing techniques, and the effects of magnetic-field annealing on the microstructure, magnetic properties, magnetisation behaviour, and corrosion resistance of MnBi are systematically investigated. The results show that the saturation magnetisation (Ms) of the Mn55Bi45 ribbons increases with increasing magnetic field annealing temperature and time. Annealing above Curie temperature (Tc) enhances the intrinsic coercivity (Hcj) of the MnBi alloy. Moreover, Mn55Bi45 ribbons with a (BH)max of 2.15 MGOe at room temperature are successfully fabricated after annealing at 673 K for 20 min. The first-order reversal curve (FORC) demonstrate that the Mn55Bi45 ribbons after magnetic-field annealing exhibits weaker exchange coupling compared with the Mn55Bi45 ribbons after nonmagnetic-field annealing. Additionally, the corrosion rate of the Mn55Bi45 ribbons after magnetic-field annealing is lower than that of the Mn55Bi45 ribbons after nonmagnetic-field annealing. Finally, the changes in the grain size and content of the MnBi phase are investigated.

Rheology of Aqueous Ferrofluids: Transition from a Gel-Like Character to a Liquid Character in High Magnetic Fields

Rheological measurements under an applied magnetic field were used to investigate the changes to the internal structure and stability of an aqueous ferrofluid. The ferrofluid was prepared by dispersing 1.8 wt.% of maghemite nanoparticles with a size of d = 14 ± 3 nm and a saturation magnetization MS = 68 emu/g in water using citric acid as the surfactant. In this study, oscillatory tests were used to investigate the internal structural changes and the stability of ferrofluid under the influence of the magnetic field B. In a magnetic field of approximately 50 mT, the G′ became higher than the loss modulus G″ as the ferrofluid exhibited a gel-like character. However, at a magnetic field of approximately 200 mT, the character of the ferrofluid reverted to that of a liquid. The change in the character of the ferrofluid in this high magnetic field was associated with a gradual change from chain agglomerates to the energetically more favourable globular agglomerates, using a calculation based on a model described in a separate work. The globular agglomerates impeded the flow to a much lesser degree than the chains, causing a reduction in the viscosity. Further increase of the magnetic field resulted in sedimentation of agglomerates and loss of magneto-rheological effect.

Correlation of the chemical composition, phase content, structural characteristics and magnetic properties of the Bi-substituted M-type hexaferrites

Bi-substituted M-type hexaferrites, BaFe12-xBixO19 (0.1 ≤ x ≤ 1.2), or Bi-BaM, were produced by the solid-state reactions. The correlation between the phase content, chemical composition, crystal structure features, and peculiarities of the magnetic properties of Bi-BaM was established using XRD (X-ray diffraction), SEM (scanning electron microscopy), and VSM (vibrational sample magnetometry). XRD phase analysis made it possible to establish the limit of substitution of Fe3+ ions by Bi3+ ions. It was shown that at a low substitution level (x ≤ 0.3), no impurity phases were detected, and the samples are characterized by a single-phase state with the space group (SG) P63/mmc. As the degree of substitution (x ≥ 0.6) increases, the formation of impurity phases was observed, which can be explained by the difficulties of ion diffusion in the process of solid-phase synthesis as well as the formation of defects in the magnetoplumbite structure due to the large ionic radius of Bi3+. As impurity phases in the studied compositions (x ≥ 0.6) the following were noted: BiFeO3 (SG: Pnma); BiO2 (SG: Fm-3m); BaBi2O6 (SG: R-3); and Ba0.5Bi1.5O2.16 (SG: Im-3m). The content of the main phase (SG: P63/mmc) decreases from 95.11 to 88.27 vol% with an increase in x from 0.6 to 1.2, respectively. Analysis of SEM images showed the growth of particles up to 10 μm, depending on the concentration of bismuth oxide during hexaferrite synthase. The Bi-BaM magnetic characteristics were examined using VSM in the range of 3 T at 300 K. Due to the magnetic structure's frustration, with increased x a decrease in saturation magnetization (Ms) was found. There were two concentration diapasons with different speeds of Ms decrease. In the first diapason, the main contribution belong to the magnetic structure frustration in the frame of the main phase (P63/mmc) due to the long-range Fe-O-Fe exchange interaction weakening (under Bi substitution). In the second diapason, the main contribution belong to the impurity phase formation and decrease of the main magnetic phase concentration in samples.

Electromagnetic Property Modulation of Flaky Ferromagnetic 304 Stainless-Steel Powders for Microwave Absorption at Elevated Temperatures

Soft magnetic metallic absorbents suffer from severe oxidation, reduction in permeability and deterioration in microwave absorption when exposed to high temperatures. In this study, we prepared flaky 304 stainless-steel powders as new microwave absorbents via deformation-induced ferromagnetism. The 304 stainless-steel powders showed significant increases in saturation magnetization (Ms) from 1.03 to 82.46 emu/g when their shape was changed from spheroids to flakes; the Ms further increased to 92.29 emu/g after heat treatment at 500 °C in air. The permeability of 304 alloy powders also showed an obvious increase after ball milling and remained roughly stable after heat treatment at 500 °C in air. Moreover, the permittivity exhibited a sharp decrease after heat treatment, enabling the improvement of impedance matching and microwave absorption. After heat treatment at 500 °C in air for 100 h, the simulated reflection loss of 304 stainless-steel powders with wax still showed attractive levels, giving a minimum value of −22 dB and remaining below −6 dB over 8.5–16.5 GHz at a thickness of 2 mm. Our work can help to include paramagnetic alloy systems as new microwave absorbents for working in harsh environments.

Interface engineering constructs oxide composite bulk γ′-Fe4N magnetic alloys with high resistivity: Superior magnetization and manufacturability

Soft magnetic material with high saturation magnetization (Ms) and high resistance (ρ) is vital to improve the power density and conversion efficient of modern electrical magnetic equipment. Yet, increasing Ms is always at the expense of high resistivity, such as soft magnetic alloys substitute for the ferrite. In this work, the superior comprehensive electromagnetic properties, namely the close association of high saturation magnetization and high resistivity, are combined in a new way in a newly Fe-N based magnetic materials. A high resistance oxide interface engineering was constructed between the conducting ferromagnetic phases in the process of spark plasma sintering (SPS) to achieve superior electromagnetic properties. The ZnO composite γ'-Fe4N bulk has a maximum resistivity of 220 μΩ cm and a Ms of up to 156.02 emu/g, while the TiO2 composite γ'-Fe4N bulk has a maximum resistivity of 379 μΩ cm and a Ms of 149.7 emu/g. The research findings offer valuable insights for the advancement of the next generation of soft magnetic materials, which hold significant potential for use in high-frequency, high-efficiency, and energy-saving power equipment applications.

FeTiB nanocrystalline films: Static and dynamic magnetic properties in accordance with phase composition and magnetic structure

Nanocrystalline Fe100–56.8Ti0–13.5B0–34.2 films 1.4 µm thick are prepared by dc magnetron deposition on glass substrates. The structure and magnetic properties of the films are comprehensively characterized and analyzed. The lattice parameter and the grain size of the bcc Fe-based phase (2-25 nm), parameters of the stochastic magnetic structure (the relative size and the effective anisotropy field of stochastic domains D1/2<Ha> and the local magnetic anisotropy field at the grain scale), saturation magnetization Ms, coercive field Hc, static permeability mst, and ferromagnetic resonance frequency fr of the films are quantitatively estimated and their interrelations are studied. As Ti and B contents increase, the phase composition of the films changes in accordance with the sequence αFe - αFe(Ti) - αFe(Ti) + TiB2 - amorphous, wherein Ms decreases from 2.1 to 0.3 T. The Hc values vary in the interval 7–70 Oe determined by the D1/2 <Ha> field or by other magnetic anisotropy sources. The μst values vary in the interval 20–140. The μst values obtained by the Lorentzian dispersion law adequately fall within the range of the calculated permeabilities, which is limited by the coercive field obtained from the hysteresis loops and the anisotropy field determined by Kittel equation. The μst values of the films are kept up to the frequencies of at least 1.5 GHz. The frequency dependences of the permeability of the films are analyzed taking into account the influence of skin effect and are considered in terms of Acher’s law. The obtained values of the Acher’s constant (less than 0.3) indicate the possibility of reaching the higher values of μst and fr at the expense of elimination of the perpendicular anisotropy, in particular, via the formation of thinner films as compared to the films under study (1.4 µm thick). According to the available literature data, the presented investigations, using the FeTiB films as an example, were performed for the first time.