Increase In Saturation Magnetization Research Articles

Martensitic phase mechanism of ternary FeCrMn thin films influenced by the substrate rotation speeds: structural and magnetic properties

In order to investigate the martensitic phase mechanism of the ternary FeCrMn thin films sputtered under the effect of substrate rotation speeds, the structural and related magnetic properties were studied. A range of thin films were deposited at varying rotational speeds of 0, 15, 30, and 45 rpm on flexible amorphous polymer substrates through the use of DC magnetron sputtering. The films were 50 nm thick and were produced at 0.09 nm s−1. The crystal structures showed that all films have a mixture of the body-centred tetragonal (bct) and tetragonal structure. The peak intensity of bct (110) martensitic α’phase increased with the increase of the rotation speeds whereas the tetragonal (430) and (333) peaks stayed almost stable. And, the morphologic surface analysis displayed that the smooth surface turned into a rough surface with the increase of the rotation speeds. After the measurements of hysteresis loops, the films obtained by sputtering of austenitic target have ferromagnetic character with increasing saturation magnetization, MS and coercivity, HC as the substrate rotation speeds increase. With increasing rotation speeds, the increase of the MS from 148 to 242 emu cm−3 and the rise of the HC of the films from 21 to 185 Oe might be explained by the increase of the grain sizes with the increase of % martensitic α’phase caused by increasing rotation speeds. The ternary FeCrMn thin films exhibit increasing % martensitic α’phase and corresponding ferromagnetic properties with increasing substrate rotation speeds. It is concluded that the nanostructured films of FeCrMn have different properties from those of their bulk counterparts under the influence of substrate rotation speeds. Therefore, the martensitic mechanism of the films can easily be controlled by changing rotation speed for potentially flexible new device applications such as spintronics, magnetic hetero-structures, magnetic separators, etc.

Exploring Microstructure and Magnetic Domain Evolution in the As-cast Soft Magnetic Fe74B20Nb2Hf2Si2 Alloy: A Comprehensive Study Using STEM, Lorentz TEM, and LM-STEM DPC Microscopy

This study delves into subtle changes in the microstructure and domain arrangement of a Fe74B20Nb2Hf2Si2 soft magnetic amorphous alloy. Utilizing transmission electron microscopy in Lorentz mode, low-magnification STEM, and differential phase contrast analysis (DPC), the research explores both the as-cast state and annealed samples. The results confirmed the formation of α-Fe, Fe23B6, Fe2(Hf, Nb), and Fe2B crystalline phases with increasing annealing temperature. Consequently, these crystallization stages induce significant alterations in magnetic domain size and spatial distribution due to microstructural changes. As the crystallization temperature rises, the volume fraction of crystalline phases increases, leading to modifications in the arrangement and size of magnetic domains. The decrease in magnetic domain size, associated with the formation of pinning sites during heat treatment, leads to alterations in soft magnetic properties. This includes an increase in coercivity (Hc) up to 40 A/m in the sample annealed at the temperature range of the third crystallization stage compared to the as-cast sample (1.5 A/m). Furthermore, as the annealing temperature rises, there is a corresponding increase in saturation magnetization (Ms), which reached to 1.71 T in the sample annealed within the temperature range of the third crystallization stage. These findings hold substantial implications for the practical applications of the Fe-based soft bulk metallic glasses (BMGs) alloy across various industries.

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.

Study on the Faraday rotation angle of La-substituted barium hexaferrite in the terahertz band

M-type barium hexaferrites (Ba1-xLaxFe12O19) were prepared by the liquid phase epitaxial (LPE) method, in which Ba2+ was substituted by La3+. The Faraday rotation effect of materials in the frequency range of 0.5–0.8 terahertz (THz) is studied by THz time-domain spectroscopy (THz-TDS). It was demonstrated that the M-type barium hexaferrites have a large Faraday rotation angle, and the Faraday rotation angle can be further enhanced by the substitution of La3+. For 500 µm thick film samples, the Faraday rotation angle exceeded 20° under the maximum measuring magnetic field of 400 mT. Moreover, the Faraday rotation angle is not saturated, and it will further increase with the increase of the magnetic field. At 0.8 THz, the Faraday rotation angle of the sample with x = 0 is 21.48°, for x = 0.05 which is 21.62°, and for x = 0.19 which is 28.38°. The Faraday rotation angle is enhanced by about 32%. By measuring the magnetic properties of the material, we found that the fundamental cause of the enhancement in the Faraday rotation angle lies in the increased saturation magnetization of the material after La3+ substitution. In the experiment, it was also found that the transmittance of the material to the THz wave decreased sharply with the increase of La substitution. For sample x = 0, the transmittance is as high as 60%. When the substitution amount of La is only x = 0.05, the transmittance decreases to about 55%. When the maximum substitution amount of La is x = 0.24, the transmittance of the material is only about 2%.

Effects of the Substitution of B and C for P on Magnetic Properties of FePCB Amorphous Alloys

In the present study, first-principles molecular dynamics simulations were employed to study the effects of small amounts of B and C substituted for P on the structure and magnetic properties of Fe80P13C7, Fe80P10C7B3, and Fe80P8C9B3 amorphous alloys. A small amount of B and C replacing P atoms increases the icosahedral structure of the amorphous alloys, especially the increase in the regular icosahedral structure. The saturation magnetization of the three kinds of amorphous alloys gradually increases with the addition of B and C atoms, and the results of experimental and simulated calculations show consistent trends. The substitution of P atoms by B and C atoms leads to the aggregation of Fe atoms, which increases the magnetic moment of the iron atoms. In addition, the improvement of local structural symmetry may be one of the reasons for the increase in saturation magnetization of amorphous alloys. The substitution of a small number of B and C atoms plays an important role in improving the saturation magnetization of the amorphous alloy, which has a certain guiding significance for the development of amorphous alloys with excellent soft magnetic properties.

Magnetic and dielectric properties of Mn2+ and Nb5+-doped NiCuZn ferrites for K-band junction circulators

Ni0.42-x/3Nbx/3Cu0.18Zn0.4MnxFe1.98−xO4−δ (x = 0–0.1) materials, possessing a high saturation magnetization, high dielectric constant, and narrow ferromagnetic resonance linewidth, were prepared via the solid-phase reaction method. The cation distribution, as well as the dielectric and gyromagnetic properties, were studied in detail. Mn2+ and Nb5+ incorporated in the lattice occupy tetrahedral site, causing the redistribution of cation and the reduction of A–B superexchange interaction. This leads to an increase in saturation magnetization followed by a decrease. The introduction of appropriate amounts of Mn2+ and Nb5+ ions reduces the magnetocrystalline anisotropy constant |K1| and thus reduces the ferromagnetic resonance linewidth (ΔH). Furthermore, high polarisability of Mn2+ and Nb5+ causes the increase in the dielectric constant of the ferrites. At x = 0.08, excellent gyromagnetic and dielectric properties, including a high dielectric constant (ε’ = 15.4@100 MHz), high saturation magnetization (4πMs = 4577 G), and narrow ferromagnetic resonance linewidth (ΔH = 129 Oe@9.55 GHz) for the NiCuZn ferrite, was achieved. Finally, a K-band microstrip circulator operating at 20.8 to 28 GHz was designed. The simulation showed that the isolation of the circulator in the working frequency band is greater than 20 dB, showing the potential of the prepared ferrites in microwave circulators.

Exploring the interplay of structure, optical, magnetic and radiation shielding properties in GeO2/Bismuth borate glasses

This article investigates the structural, chemical, optical, and magnetic properties of borate bismuth glasses doped with increasing GeO2 concentrations. X-ray diffraction (XRD), Raman spectroscopy, density measurements, thermal analysis, UV–Vis absorption, and VSM studied the impact of GeO2 on the glass network. The XRD results of the study confirmed that glass is amorphous. The bulk density increased while the molar volume decreased with increasing GeO2 concentration. Glass transition temperature (Tg) slightly decreases due to weaker Ge–O bonds and lower cross-linking density. Crystallization temperature (Tc) increased as GeO2 disrupts the network, hindering crystal nucleation and growth. Optical band gap narrows with increasing GeO2, with direct and indirect gaps decreasing. Urbach energy (EU) rises with GeO2, indicating increased disorder in the glass network. Refractive index (n) and extinction coefficient (k) both increased with GeO2, attributed to non-bridging oxygen formation. VSM measurements reveal an increase in saturation magnetization from 0.1 to 0.3 emu/g with increasing GeO2 content. Mass attenuation coefficient (MAC) and linear attenuation coefficient (LAC) investigations showed the efficiency of the glass system for radiation attenuation at varying energies. The unique properties of these borate bismuth glasses doped with GeO2 show promise for various technological advancements in optoelectronics and radiation shielding.

Influence of particle size on the magnetic and microwave absorption properties of magnetite via mechano-mechanical methods for micro-nano-spheres

The demand for innovative electromagnetic wave absorbers stems from the pressing need to mitigate electromagnetic interference and pollution emanating from electronic devices and communication technologies, which pose risks to human health and disrupt the functionality of electronic equipment. This study investigates how particle size influences the magnetic and microwave absorption properties of magnetite micron-nano-spheres. Utilizing ball milling (BM) and mechanochemical alloying (MA), particle sizes were controlled by varying the milling times, resulting in a reduction of magnetite's average particle size from 3 µm to 43 nm. The research uncovers the unique effects of blending micron and nano-sized particles, a phenomenon previously undocumented. It was observed that saturation magnetization and coercivity increase with larger particle sizes due to the small size effect. The complex permittivity, dielectric loss and attenuation constant of the magnetite nanocomposites were influenced by the larger interface area and increased defects in smaller-sized nano-filler composites. Decreasing the magnetite particle size leads to a lower frequency shift and a broader bandwidth of the reflection loss (RL) peak in the fixed absorber, with maximum RL achieved for thinner absorber layers. Notably, the mixed micron-nano magnetite composite exhibits promising microwave absorption capabilities, achieving a maximum RL of −35.36 dB at 16.8 GHz with a 1 mm thickness, making it suitable for lightweight microwave absorption. Resonance frequencies corresponding to RL below −20 dB extend to 3.63 GHz, meeting the 99 % wave absorption requirement due to the high loss tangent of antiferromagnetic resonance and significant magnetic relaxation peak over the 8–18 GHz frequency range. This study underscores the significant impact of adjusting the particle size on microwave absorption properties, where decreasing the size broadens the absorption bandwidth, shifts the RL peak to lower frequencies and maximizes RL with thinner thicknesses. Increasing the nano-filler content enhances the absorption bandwidth and microwave absorber performance by augmenting the dielectric loss, attenuation constant and impedance matching. Overall, controlling the particle size proves effective in tailoring microwave absorption, highlighting the potential of magnetite composites as ultra-thin, lightweight materials capable of absorbing a wide range of microwave frequencies. These composites find applications in microwave absorption, stealth technology and managing electromagnetic interference, leveraging the magnetic properties of ferrites and exploiting super-exchange interactions in microparticles-sized materials. Moreover, they benefit from the amplified dielectric or/magnetic losses resulting from the characteristics of nanoparticle-sized materials, including high surface area, greater surface atoms and multiple reflections, resulting in exceptional microwave absorption performance exceeding 99 % across an exceptionally broad bandwidth.

Impact of Co and Cu co‐doping on the Structural, Electrical, Magnetic and Solar Light Driven Photo‐Catalytic Properties of NiFe2O4 Nano‐crystals for Crystal Violet Dye Removal

AbstractHerein, we have synthesised cobalt (Co) and copper (Cu) co‐doped Ni‐ferrite Ni1‐xCoxFe2‐yCuyO4 nanocrystals (NCs) via the facile micro‐emulsion method. The materials were analysed for various physio‐chemical characterizations to investigate the co‐doping (Co and Cu) effects on magnetic, structural, electrical, photo‐catalytic properties. The structural analysis via Fourier Transform Infrared spectroscopy (FTIR) and X‐rays diffraction (XRD) showed the successful fabrication of Co and Cu co‐doped materials with cubic spinel geometry having a single phase, the crystallite size was observed in 15 to 24 nm range. The electrical response measured using current‐voltage (I–V) analysis showed good electrical features, the electrical resistivity declined from 6.85×107 Ohm.cm for un‐doped materials to 0.04×107 Ohm.cm for co‐doped materials, which was accredited due to the synergistic effects of Co and Cu metal cations in co‐doped Ni‐based ferrite structures. Magnetic investigation using VSM analysis showed increased saturation magnetization (Ms 31.32 to 50.75 emu/g) and coercivity (218.76 to 406.82 Oe) because of the higher magnetic responses of Co2+ions in the co‐doped spinel ferrite NCs. BET surface‐area analysis showed good porosity for co‐doped materials with an increased surface area of 52 to 104 m2/g on co‐doping. The Tauc's plot described the decline of band‐gap energies value (Egs) (1.99 eV) in co‐doped (x=y=0.56) materials as compared to (2.16 eV) of the un‐doped NiFe2O4 materials, which is due to more electrical responses of Co and Cu co‐dopant cations that possess higher energy levels, which can stabilize the charge carrier‘s species. Furthermore, the photo‐degradation using solar light showed good removal of crystal violet (CV) dye, which was almost 94.14 % by co‐doped material; however, by un‐doped material, it was 38.044 %. The scavenger experiment shows that the (OH⋅) hydroxyl radicals and (e−/h+) species play a prime role in the degradation of CV dye. Recycling and recoverability tests for five cycles’ exhibited outstanding stability of the photocatalyst with only 1.7 % losses in activity. Overall, our results showed that co‐doped Ni1‐xCoxFe2‐yCuyO4 NCs materials exhibited enhancement in the magnetic, electrical, photo‐catalytic properties and a decline in band‐gap energy values as compared to un‐doped NiFe2O4, which might have potential use in magnetic and electrical devices as well as solar‐driven photo‐catalyst materials for the remediation of environmental pollution.

Synthesis of Dy-doped calcium hexaferrite (CaDyxF12-xO19) nanoparticles and their ferroelectric, dielectric, magnetic and photocatalytic properties under solar light irradiation

Calcium hexaferrite (CaDyxFe12-xO19) was synthesized using the microemulsion method, incorporating Dy as a dopant at varying levels (x = 0.00, 0.1, 0.15, 0.20, 0.25, and 0.30). The effects of Dy-doping on the structural, magnetic, ferroelectric, dielectric and photocatalytic properties of CFO (CaDyxFe12-xO19) was evaluated. X-ray diffractometer, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV–vis spectroscopy were employed for the characterization of the prepared samples. A single-phase hexagonal structure with space group P63/mmc was verified by the XRD analysis and the crystallite size was in the 31.74 nm to 38.77 nm range. The ferroelectric properties were examined using a hysteresis loop (P-E), revealing that higher dopant concentrations led to decreased saturation polarization (Ps) and retentivity (Pr). Electrical studies, including I-V measurements, aligned with semiconductor behavior, as evidenced by Curie temperature and activation energy values. Magnetic assessments demonstrated increased saturation magnetization (0.028–0.049 emu/g) and remanence (0.0046–0.0144 emu/g) upon Dy-doping. Photocatalytic experiments exhibited promising crystal violet dye degradation under visible light irradiation, with highly doped catalyst showing 85 % degradation within 100 minutes, surpassing the 42 % degradation with pristine CaFe12O19. The synthesized nanoparticles demonstrated promising stability and reusability in recycling experiments. Investigation of scavenger effects highlighted the crucial role of reactive •OH in dye degradation, surpassing the contributions of e- or h+ species. The CaDyxFe12-xO19 holds significant potential for efficient photocatalytic application in the removal of dyes from effluents under visible light irradiation.

Static Magnetic Properties and Morphological Behaviour of Mn and Zn Substituted Ca-hexaferrite by Ceramic Technic

Synthesis of M-type hexagonal ferrite compounds, Ca(CoTi)0.5(MnZn)x/2Fe11-xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) prepared by ceramic technic. Mn and Zn ions substituted to find the magnetic characterizationat magnetic field of 10 kOe. XRD and SEM study have been done for getting the hexagonal structure of these samples. Due to the substitution of Mn and Zn ions saturation magnetization increases and magnetocrystalline anisotropy decreases. Due to the sub-latice site distribution the variations in magnetic parameters have been observed. Because of Mn and Zn ions substitution Curie temperature decreases by weakening of superexchange interaction. These materials can be used for various applications such aspermanent magnetic material, magnetic recording media, ferrofluids, sensors, microwave absorbing materials, ceramic magnets in loud speakers and rotors in small DC motors by studying various magnetic parameters from VSM characterization.

Modification induced by electronic excitation in CoFe2O4 thin films: Structural, morphological, and magnetic properties

AbstractThe present study focuses on the modification induced by 200 MeV Ag15+ and 100 MeV O7+ ion irradiations on the structural, surface morphological, and magnetic properties of radio frequency sputtered CoFe2O4 (CFO) thin films grown on SiO2/Si (100) substrates. X‐ray diffraction shows amorphization of the CFO thin films when irradiated with Ag ions and varies with fluences. This effect is absent in the case of O ion irradiated CFO films. These results are consistent with the measurements from the Raman spectroscopy, where the intensities of Eg and T2g modes are significantly reduced and further disappear in the high fluence. The surface morphology of the O ion irradiated films is dramatically different from the pristine and Ag ion irradiated films where the surfaces appear in nanopillars‐like patterns. The topography of the O ion irradiated films appears to be like hill and valley structures, the roughness first increases (from 10.11 to 24.39 nm). Then it decreases to 18.93 nm on further increasing ion fluence. The coercivity, remnant magnetization, and saturation magnetization increase upon irradiation at low fluence 5 × 1011 ions/cm2 for both the ion beams and then downturn with the increase of fluence 5 × 1012 ions/cm2. The changes in the magnetic and structural characteristics are ascribed to the defects induced by ion irradiation. These results are understood based on the structural and surface modifications induced by the electronic excitation of Ag and O ions. The study depicts that a controlled selection of ions and beam fluence can tailor the structure, morphology, and magnetic properties of ferrite films.

Synthesis, Surface Modification and Magnetic Properties Analysis of Heat-Generating Cobalt-Substituted Magnetite Nanoparticles.

Here, we present the results of the synthesis, surface modification, and properties analysis of magnetite-based nanoparticles, specifically Co0.047Fe2.953O4 (S1) and Co0.086Fe2.914O4 (S2). These nanoparticles were synthesized using the co-precipitation method at 80 °C for 2 h. They exhibit a single-phase nature and crystallize in a spinel-type structure (space group Fd3¯m). Transmission electron microscopy analysis reveals that the particles are quasi-spherical in shape and approximately 11 nm in size. An observed increase in saturation magnetization, coercivity, remanence, and blocking temperature in S2 compared to S1 can be attributed to an increase in magnetocrystalline anisotropy due to the incorporation of Co ions in the crystal lattice of the parent compound (Fe3O4). The heating efficiency of the samples was determined by fitting the Box-Lucas equation to the acquired temperature curves. The calculated Specific Loss Power (SLP) values were 46 W/g and 23 W/g (under HAC = 200 Oe and f = 252 kHz) for S1 and S2, respectively. Additionally, sample S1 was coated with citric acid (Co0.047Fe2.953O4@CA) and poly(acrylic acid) (Co0.047Fe2.953O4@PAA) to obtain stable colloids for further tests for magnetic hyperthermia applications in cancer therapy. Fits of the Box-Lucas equation provided SLP values of 21 W/g and 34 W/g for CA- and PAA-coated samples, respectively. On the other hand, X-ray photoelectron spectroscopy analysis points to the catalytically active centers Fe2+/Fe3+ and Co2+/Co3+ on the particle surface, suggesting possible applications of the samples as heterogeneous self-heating catalysts in advanced oxidation processes under an AC magnetic field.

Magnetic properties and microstructure of Ce and Zr synergetic stabilizing Ti-lean SmFe12-based strip-casting flakes

Recently ThMn12-type samarium iron alloys have been promising materials for permanent magnets. Due to the high abundance and low cost, Ce as a possible stabilizer can be introduced into ThMn12-type alloys. The effect of Ce doping on the magnetic moment and phase stability in Ti-lean (Ce,Sm,Zr)(Fe,Co,Ti)12 compounds were predicted by the first-principles calculations. The CexSm0.8-xZr0.2(Fe0.8Co0.2)11.5Ti0.5 (x = 0–0.8) alloys with ThMn12 structure were produced by strip-casting into flakes by a wheel speed of 1.5 m/s and annealed at 1000 °C for 24 h. The Ce0.8Zr0.2(Fe0.8Co0.2)11.5Ti0.5 annealed flake shows a high saturation magnetization value of 13.6 kGs at room temperature. With the increase of Ce substitution in the annealed flakes, the content of α-(Fe,Co,Ti) phase decreases and the saturation magnetization increases. The 1:12 phase and the 1:9 phase have an orientation relationship that can be expressed as [0 0 –1]1:12//[100]1:9 and (020)1:12//(010)1:9. Besides, annealing process promotes the formation of 1:12 phase transformed from 1:9 phase. Coercivity is expected to be improved by obtaining uniform microstructure and suppressing the formation of soft α-(Fe,Co,Ti) phase in the ThMn12-based alloys.

Enhancing ferromagnetism in the Sm(Co, Mn)5 system: Impact on phase stability and magnetic properties

This work demonstrates that Mn can be a beneficial candidate for the performance modulation of permanent magnetic materials like SmCo5. Theoretical calculations reveal that Mn has a large positive contribution to the magnetization of SmCo5, owing to the strong ferromagnetic exchange interaction between Co and Mn atoms. It is also found that Mn could occupy both 2c and 3g crystal sites because of the minute energy difference between them can be easily overcome through thermal activation. Co atoms on the same site with Mn have increasing moments with the increase in Mn content, whereas those on the other sites show decreasing moments. The experimental substitution of Mn for Co leads to a contraction of the SmCo5 single-phase region, and thus pure Sm(Co, Mn)5 phase could only be obtained through subtle control of Sm content by annealing. Significantly, a 13 % increase in saturation magnetization of SmCo5 is achieved through Mn substitution. A slight rise in the Curie temperature is also obtained, suggesting that Mn substitution does not strongly disturb the exchange interactions of the Co sublattice. This study offers a new option for enhancing magnetic properties in Sm–Co systems and introduces novel physical phenomena resulting from Mn substitution, which is worthy of further investigation.

Wet synthesis of magnetically retrievable Mn/Nd co-doped cobalt ferrites for visible light-driven photocatalytic annihilation of azo dye

In this study, a surfactant assisted wet-chemical method was used to synthesize manganese and neodymium co-doped cobalt ferrite [Co1-xFe2-y O4 (x = Mn, y = Nd)]. The co-doping strategy was adopted to enhance the magnetic properties, tune the band gap, and hamper charge–recombination in the spinel ferrite during the photocatalytic application. Different dopant concentrations, namely Mn = Nd = 1.1 %, 2.2 %, 3.3 %, and, 4.4 %, were used to synthesize MNCF-1, MNCF-2, MNCF-3, and MNCF-4 samples, respectively. The pristine (CF) and co-doped samples (MNCF) were characterized via TGA, PXRD, Raman, FTIR, and UV/Vis techniques to examine the impact of co-doping on the various physicochemical and thermal properties. The optical study proposed the MNCF-4 sample with a band gap value of 2.88 eV as most suitable for visible-light harvesting. A dielectric study showed that co-doped ferrite with a higher dopant concentration (MNCF-4) exhibits boosted AC conductivity and substantially decreased leakage current as compared to the bare and co-doped samples. As the concentrations of the co-dopants increase, the coercivity field (Hc) decreases while the remanent magnetization (Mr) and saturation magnetization (Ms) increase. The MNCF-4 material exhibited the highest magnetic properties, ensuring its full and quick magnetic recovery at the completion of the photocatalytic process. In the context of photocatalytic applications, it was observed that the MNCF-4 catalyst exhibited a mineralization rate constant value of 0.016 min−1 for 92.5 % crystal violet (CV) dye. To mitigate the impact of dye sensitization, the photocatalytic efficiency of MNCF-4 material was assessed by using phenol as a representative colourless organic pollutant. The enhanced magnetic properties of the MNCF-4 catalyst enable its complete magnetic recovery and 90.2 % retention of the photocatalytic activities after five reusability tests.

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.

Tuning the magnetic properties of hard–soft Ba0.5Sr0.5Fe10Al2O19 and Ni0.1Co0.9Fe2O4 nanocomposites via one pot sol–gel auto combustion method for permanent magnet applications

Permanent magnets generate magnetic fields that can be sustained when a reverse field is supplied. These permanent magnets are effective in a wide range of applications. However, strategic rare-earth element demand has increased interest in replacing them with huge energy product (BH)max. Exchange-coupled hard/soft ferrite nanocomposites have the potential to replace a portion of extravagant rare earth element-based magnets. In the present, we have reported the facile auto combustion synthesis of exchange-coupled Ba0.5Sr0.5Fe10Al2O19 and Ni0.1Co0.9Fe2O4 nanocomposites by increasing the content of soft ferrite over the hard from x = 0.1 to 0.4 wt%. The XRD combined with Rietveld analysis reflected the presence of hexaferrite and spinel ferrite without the existence of secondary phases. The absorption bands from the Fourier transform infrared spectrum analysis proved the presence of M–O bonds in tetrahedral sites and octahedral sites. Rod and non-spherical images from TEM represent the hexaferrite and spinel ferrite. The smooth M–H curve and a single peak of the switching field distribution curve prove that the material has undergone a good exchange coupling. The nanopowders displayed an increase in saturation magnetization and a decrease in coercivity with the increases in the spinel content. The prepared nanocomposites were showing higher energy products. The composite with the ratio x = 0.2 displayed a higher value of (BH)max of 13.16 kJ m−3.

Study of structural, X-ray photoelectron spectroscopy, Raman and temperature-dependent magnetic studies of NiFe2O4/CoCr2O4 nanocomposites

In recent years, cobalt chromites/nickel ferrites have been attractive candidates for significant applications as nanomagnets. In the present work, structural, electronic, vibrational and low-temperature magnetic properties of NiFe2O4, CoCr2O4, and NiFe2O4/CoCr2O4 nanocomposites were investigated. Refined XRD patterns and the Raman spectra confirm the formation of the pure crystalline spinel cubic phase. The estimated crystallite size is in the range of 14 - 29 nm. X-ray photoelectron spectroscopy (XPS) confirm the oxidation state of all elements present in the synthesized samples. The studies of the photoemission core level lines prove the cations distribution in the tetrahedral and octahedral sites with the expected valence states. The magnetic studies reveal the S-type hysteresis loops, confirming the ferrimagnetic nature. The remanent and saturation magnetization increase with increasing NiFe2O4 concentration and decrease with increasing temperature. The magnetization also increases with increase of crystallite size. The temperature-dependent magnetization curve of CoCr2O4 shows the ferrimagnetic phase transition at Curie temperature TC = 86 K. The performed density functional theory (DFT) calculations indicate a significant distribution of the density of states over the Fermi level in NiFe2O4/CoCr2O4 composites as compared to bare NiFe2O4 and CoCr2O4 materials, confirming the improved electronic properties. The overall magnetic analysis proved the magnetization enhancement by increasing x concentration.

Quantifying the characteristics of magnetic oil–water contacts in mature hydrocarbon reservoirs and their capacity for understanding hydrocarbon remigration

SUMMARY Increasing magnetization within mature hydrocarbon reservoirs provides a new technique in identifying oil–water contacts (OWCs) in cored wells with the potential to assess yield thereby reducing the need for further exploration. Authigenic precipitation of magnetic minerals at OWCs may also help locate palaeocontacts (PCs), where structural changes to the petroleum system have caused hydrocarbon remigration. This study determines the magnetic characteristics of magnetic enhancements at OWCs and possibly PCs in silliclastic and carbonate reservoirs at the Wytch Farm oil field, Wessex Basin, UK. Increases in saturation magnetization and susceptibility are observed at the OWC in 11 of the 12 analysed cored reservoirs owing to the increased presence of magnetite and vivianite. Geochemical analysis and shallow reservoirs suggest biogenic and inorganic mineral precipitation is extensive at the OWC depending on iron, sulphur and phosphorus availability. Similar magnetic characteristics have been observed in magnetic enhancements above the OWC in numerous wells which may represent OWCs before a basin-wide easterly tilt caused hydrocarbon remigration in the Cenozoic. Multiple magnetic enhancements above the OWC in westerly onshore wells, suggest this remigration may have occurred as numerous phases.