Magnetic Applications Research Articles

Observation of Griffiths phase and giant magnetocaloric effect in double perovskite oxide RE2FeCrO6 (RE = Gd, Tb, Dy, Er)

AbstractThe magnetic properties of double perovskite oxide RE2FeCrO6 (RE = GD, Tb, Dy, Er) were systematically studied, and the Griffiths phase evolution was observed. In Tb2FeCrO6, Dy2FeCrO6, and Er2FeCrO6, there are antiferromagnetic (AFM)‐ferromagnetic (FM) first‐order phase transition and the Griffiths phase with coexistence of FM and paramagnetic (PM) was observed by the EPR spectra. Gd2FeCrO6 has an AFM–PM second‐order phase transition, and there is no first‐order phase transition in the range of ∆H = 0–50 kOe. As the temperature decreases, all four sets of samples present χ−1 (T) deviates downwards from the Curie–Weiss linear behavior from 0.2 to 5 kOe, corresponding to the typical characteristics of Griffiths phase evolution. In addition, all four sets of samples have excellent magnetocaloric performance. Especially, the Gd2FeCrO6 oxide has giant magnetic entropy change and relative cooling power (−∆SMmax = 30.31 J/kg K and RCP = 312.8 J/kg when ∆H = 50 kOe). From the perspective of low‐temperature magnetic refrigeration application, the present work provides important candidate references for magnetic component researchers.

Synthesis and Characterization of Cu-Co Substituted Strontium Hexaferrite for Magnetic Applications

In this study, the structural and magnetic characterizations of a series of SrCoxCuxFe12-2xO19; 0.0 ≤ x ≤ 0.5 samples, which were produced by the conventional ceramic method, were carried out. The structure was examined by X-ray diffraction (XRD) technique and optical microscopy. A vibrating sample magnetometer (VSM) was used to characterize the ferrimagnetic properties. XRD patterns confirmed the presence of a single phase as Sr-hexaferrite while there were not any peaks of unreacted Fe2O3 phase. The densities varied between 92 – 98 %. XRD patterns of the Sr-hexaferrite samples were slightly modified because of the co-substitution of Cu-Co; however, the magnetic properties changed remarkably. The sample with Cu-Co of x = 0.1 content had the highest saturation magnetization (33.52 emu/g), remanence (19.74 emu/g), and coercivity (4.3 kOe). The synthesized magnetic samples were found to be suitable for the development of attractive ferrimagnetic properties for the current ferrite magnets.

Experimental study on the critical current in highly flexible REBCO cables under copper tube compaction

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) is developing the high-current REBCO cable-in-conduit conductor (CICC) for use in the Central Solenoid (CS) coil of the next generation nuclear fusion device. The aim is to develop a CICC comprising six REBCO sub-cables to satisfy the requirements of operation with a current of around 46 kA and a peak field of up to 20 T. Sub-cables, as crucial components within CICCs, play a pivotal role in ensuring the mechanical support strength and current-carrying stability of the entire CS coil system. Therefore, a process was developed in this paper for the first time to make a sub-cable that meets the requirements by inserting the Highly Flexible REBCO Cable (HFRC) cable into a copper tube and compacting it. Meanwhile, the feasibility and reliability of this process were evaluated and optimized using experimental methods at 77 K and self-field. The result indicated that sub-cables without copper tape protection experienced a 25.42% degradation in critical current (IC). In contrast, when at least one protective layer of copper tape was used as a protective buffer between the HFRC cable and the inner wall of the copper tube, the IC remained stable within a 1% error margin after compaction. These findings demonstrate the feasibility of this sub-cable preparation process. Meanwhile, this compaction method provides a solid process foundation for the development of full-size conductors in future magnet applications.

Lithospheric magnetic structure of cratonic regions in Central-Eastern China inferred from aeromagnetic anomalies: Insights into magnetization in the uppermost mantle

Most of the subcontinental lithospheric mantle (SCLM) beneath Proterozoic cratons consists of refertilized Archaean SCLM. Variations in SCLM composition and its physical properties significantly affect the stabilization and preservation of the ancient continents. In this paper, aeromagnetic data are analyzed to reveal the magnetic structure of the lithospheric mantle beneath two major Precambrian blocks in central-eastern China, i.e., the Upper Yangtze Block (UYB) and Ordos Block (OB). After being reduced to the pole, the Fourier power spectrum of the aeromagnetic anomalies is calculated to determine the depth to magnetic sources. Considering the lower spatial resolution of the power spectral analysis in dealing with the long-wavelength aeromagnetic anomalies, we applied the scale-normalized continuous wavelet transform (CWT) on the magnetic data to trace the magnetic sources, with special focus on deeper ones. Synthetical model of a magnetic layer and application to the profile data validate the effectiveness of this scale normalization scheme in improving the wavenumber/spatial resolution in the CWT scalogram.In order to present a detailed magnetic structure, we carried out 2.5D forward modeling work on the magnetic data of a 2280 km-long nearly N-S profile across the UYB and OB. Due to the inherent ambiguity in the modeling results, the CWT-based spectral analysis is successfully adopted to provide source depth constraints for the initial model. The constrained forward modeling results indicate strong inhomogeneities among main tectonic blocks of studied area, like humans have different fingerprints. The magnetization of OB is larger than that of UYB since its Archean to Paleoproterozoic metamorphic basement are widely exposed at the surface, while the Precambrian basement of UYB is mostly overlain by unmetamorphosed Sinian cover and weakly metamorphosed Neoproterozoic strata. The most interesting aspect is that deep-seated magnetic sources might reside in the uppermost mantle of UYB and OB, suggesting vertical layering in the SCLM in cold cratonic regions.

Mn doping nanoarchitectonics of NiO nanoparticles with various property impacts for optoelectronic devices and diluted magnetic semiconductor applications

Mn doping nanoarchitectonics of NiO nanoparticles with various property impacts for optoelectronic devices and diluted magnetic semiconductor applications

Synergetic effect of Hexaferrite and reduced Graphene oxide (rGO) in Photothermal therapy and Hyperthermia applications

This research article describes the synthesis of composite materials by combining T-type hexagonal ferrite and reduced Graphene Oxide using the standard ceramic process. The Calcium-based T-type hexagonal ferrite was synthesized by using the sol-gel auto-combustion method whiles the reduced graphene oxide by adopting the Hummer method. The crystallite size varied in the range of 34.11 to 42.07nm as calculated from the X-ray diffraction (XRD) data. Consequently, the lattice parameters 'a' and 'c' decreased from 5.9 to 5.1Å and from 29.92 to 28.32Å, respectively. The use of atomic force microscopy (AFM) revealed a range of particle sizes at the surface, varying from 1.70nm to 3.85nm. Moreover, the saturation and remanence magnetization values demonstrated an increasing trend with T-type hexaferrites concentration whereas the coercivity decreased. The UV-vis near-infrared spectra exhibited substantial light absorption, characterized by a wide absorption range in the visible and near-infrared (NIR) region (700 to 1100nm) which indicates its use in Photothermal therapy (PTT). The Calcium T- type hexaferrite exhibited clear peaks in the blue, green, violet, and yellow spectra in its photoluminescence (PL) properties. These peaks are believed to be caused by oxygen vacancies and defects. The synthesized samples displayed a lossy behavior in the polarization-electric field (P-E) loop, with saturation polarization levels exceeding remnant polarization, which is an amenable condition for lossy behavior. Most importantly, the synthesized materials had significant thermal responses when exposed to an alternation (AC) magnetic field, indicating their potential use in magnetic hyperthermia applications.

Investigation on Magnetic Hysteresis Loss of REBCO Twisted Stack Slotted-Core Cable for Fusion Magnet Application

Investigation on Magnetic Hysteresis Loss of REBCO Twisted Stack Slotted-Core Cable for Fusion Magnet Application

Iron-Based Superconductors for High-Field Applications: Realization of High Engineering Critical Current Density

Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (Je) is a key parameter for measuring the maximum current density that superconducting materials can withstand in practical applications. It serves as a bridge between theoretical research and practical applications of superconductors and has great significance in promoting the development and application of superconducting technology. In this study, Ag sheathed Ba0.6K0.4Fe2As2 (Ba-122) iron-based superconducting tapes were prepared by using the process of drawing, flat rolling and heat treatment by hot pressing (HP). For the first time, the filling factor of the tapes increased to about 40%, leading to a reduction in the volume fraction of Ag, consequently lowering the overall cost. The optimal parameters for achieving high transport Je were obtained by comparing the effects of different HP pressures on the properties and micro-morphology of the tapes. The prepared mono-filament tapes are capable of carrying the transport Je of 4.1 × 104 A/cm2 (Ic = 350 A) at 4.2 K, 10 T, marking the highest Je reported for Ba-122 wires and tapes to date. Our results show that high transport Je can be obtained in Ba-122 superconducting tapes, and iron-based superconductors have a promising future in practical applications.

A numerical comparison of Gd, Pr0.65Sr0.35MnO3 and single LaFeCoSi for use in a magnetic refrigeration.

Abstract One of the most significant scientific difficulties to achieving excellent performance for room-temperature magnetic cooling devices is finding suitable magnetocaloric refrigerants. To contribute to this research field, three kinds of magnetocaloric materials (Gd, Pr0.65Sr0.35MnO3 and single LaFeCoSi) in the same conditions (Curie temperature, applied magnetic field) have been considered to evaluate their potential in the magnetic refrigeration application using a 1D-AMRR (Active-Magnetic-Refrigeration-Regenerator) cycle with a parallel plate regenerator. In this way, four cooling performance parameters were investigated, namely the temperature span, the cooling power, the exergy, and the coefficient of performance. The temperature span was found to be 11.79K for Gd , 8K for LaFeCoSi and 4.47 K for Pr0.65Sr0.35MnO3. The obtained numerical results reveal that the Gd-based AMR system displays a higher efficiency, while the Pr0.65Sr0.35MnO3-based AMR system exhibits a smaller one. The magnetocaloric effect (MCE) in the magnetic refrigerants was considered to explain the result obtained and can be considered as one of the main factors to enhance the magnetic refrigeration performance.

Ovarian–Adnexal Reporting and Data System (O-RADS) MRI Scoring: Diagnostic Accuracy, Interobserver Agreement, and Applicability to Machine Learning

Abstract Objectives To evaluate the interobserver agreement and diagnostic accuracy of ovarian–adnexal reporting and data system magnetic resonance imaging (O-RADS MRI) and applicability to machine learning. Material and methods Dynamic contrast-enhanced pelvic MRI examinations 471 lesions were retrospectively analyzed and assessed by three radiologists according to O-RADS MRI criteria. Radiomic data were extracted from T2, and post-contrast fat-suppressed T1-weighted images. Using these data, an artificial neural network (ANN), support vector machine, random forest, and naive Bayes models were constructed. Results Among all readers, the lowest agreement was found for the O-RADS 4 group (kappa: 0.669 (95% confidence interval [CI] 0.634–0.733)), followed by the O-RADS 5 group (kappa: 0.709 (95% CI 0.678–0.754)). O-RADS 4 predicted a malignancy with an area under the curve (AUC) value of 74.3% (95% CI 0.701–0.782), and O-RADS 5 with an AUC of 95.5% (95% CI 0.932–0.972),(p < 0.001). Among the machine learning models, ANN achieved the highest success, distinguishing O-RADS groups with an AUC of 0.948, a precision of 0.861, and a recall of 0.824. Conclusion The interobserver agreement and diagnostic sensitivity of the O-RADS MRI in assigning O-RADS 4–5 were not perfect, indicating a need for structural improvement. Integrating artificial intelligence into MRI protocols may enhance their performance. Advances in knowledge Machine learning can achieve high accuracy in the correct classification of O-RADS MRI. Malignancy prediction rates were 74% for O-RADS 4 and 95% for O-RADS 5.

Magnetic properties and magnetocaloric effect in thiospinel Fe1-xCuxCr2S4 (x = 0.0, 0.5) compounds

In this study, we investigate the magnetic and magnetocaloric properties of Cr-based spinel sulphides Fe1-xCuxCr2S4 (x = 0.0 and x = 0.5). The magnetic transition temperature of FeCr2S4 (176 K) increases to 330 K when 50 % of Fe in FeCr2S4 structure is substituted with Cu. Temperature-dependent Zero-Field-Cooled (ZFC) and Field-Cooled (FC) magnetic moment measurements show a paramagnetic (PM) to ferrimagnetic (FiM) phase transition in our samples. Magnetocaloric properties were investigated through magnetization isotherm measurements. The maximum magnetic entropy change values are −2.78 J/kg. K and −2.11 J/kg. K under 5 T magnetic field, for x = 0 and x = 0.5 in Fe1-xCuxCr2S4, respectively. Analysis of phenomenological universal curves and Arrott plots indicate a second-order magnetic transition for both compounds. Consequently, Fe0.5Cu0.5Cr2S4 emerges as a promising candidate for magnetic refrigeration applications due to its considerable high magnetic entropy change and its proximity to room temperature transition.

Preparation for a Novel N-Doped Magnetic Sludge-Based Biochar and Application for Norfloxacin Removal from Wastewater

Preparation for a Novel N-Doped Magnetic Sludge-Based Biochar and Application for Norfloxacin Removal from Wastewater

Analysis of Magnetization Dynamics in NiFe Thin Films with Growth-Induced Magnetic Anisotropies

We have used angled magnetron sputter deposition with and without sample rotation to control the magnetic anisotropy in 20 nm NiFe films. Ferromagnetic resonance spectroscopy, with data analysis using a Bayesian approach, is used to extract material parameters relating to the magnetic anisotropy. When the sample is rotated during growth, only shape anisotropy is present, but when the sample is held fixed, a strong uniaxial anisotropy emerges with in-plane easy axis along the azimuthal direction of the incident atom flux. When the film is deposited in two steps, with an in-plane rotation of 90 degrees between steps, the two orthogonal induced in-plane easy-axes effectively cancel. The analysis approach enables precise and accurate determination of material parameters from ferromagnetic resonance measurements; this demonstrates the ability to precisely control both the direction and strength of uniaxial magnetic anisotropy, which is important in magnetic thin-film device applications.

Enhanced magnetocaloric effect in nano-sized Dy3Ga5O12 garnet: A comparative study on the effect of solid-state and wet-chemical synthesis

This study investigates the magnetic and structural properties of bulk and nanosized Dy3Ga5O12 (DGG) synthesized through solid-state and wet chemical methods to assess the impact of particle size. The single-phase composition of the synthesized materials was determined by X-ray diffraction analysis (XRD). XRD and TEM analysis revealed the formation of nanosized DGG via the wet chemical route at 750 °C/2h. The nano DGG exhibits enhanced magnetocaloric effect compared to its bulk counterpart, suggesting its potential as a promising material for low-temperature magnetic refrigeration applications.

Applications of paleomagnetism and rock magnetism in understanding volcanic processes and timescales: perspectives to Korean volcanological research

Applications of paleomagnetism and rock magnetism in understanding volcanic processes and timescales: perspectives to Korean volcanological research

The designing of magnetic nanomaterials synthesis and applications in dye degradation: a review.

Numerous activities, including rapid industrialization, population increase, and agricultural practices, have continuously contaminated freshwater resources. One of the main risks to aquatic life and human health is water pollution, which can lead to a number of extremely dangerous illnesses, includingcancer, asthma, and gastrointestinal problems. The contaminated wastewater could be cleaned using a variety of traditional and cutting-edge techniques. In order to solve these problems, scientists have been investigating a number of treatment techniques, such as adsorption, which uses adsorbents to effectively and selectively remove particular pollutants. Adsorption is the most widely used economical and effective method for treating wastewater and eliminating dangerous contaminants. The surface characteristics of the adsorbents utilized, such as their surface area and availability of functional groups, are what primarily determine the efficacy of adsorption. Since different carbon derivatives derived from waste are used as adsorbents to remove harmful pollutants, nanomaterials have been used as effective adsorbents in recent times because of their superior surface qualities. Particularly magnetite (Fe3O4), magnetic adsorbents have shown great promise as an adsorbent material for water filtration. It is appropriate for the adsorption of numerous pollutants due to its large surface area, supermagnetism, and simplicity of functionalization. In order to eliminate harmful contaminants including heavy metals, dyes, pesticides, and polycyclic aromatic hydrocarbons from wastewater, this review paper critically examined the synthesis of nanomaterials, with a focus on green synthesis. It is anticipated that this kind of multidisciplinary research would lead to more advancements in advanced nanotechnology and nanoscience in the water treatment industry.

Predicting Electrical Conductivity in Bi-Metal Composites.

Generating high magnetic fields requires materials with not only high electric conductivity but also good strength properties in order to withstand the necessarily strong Lorentz forces. A number of bi-metal composites, most notably Cu/Nb, are considered to be good candidates for this purpose. Here, we generalize our previous work on Cu/Nb in order to predict, from theory, the dependence of electric conductivity on the microstructure and volume fraction of the less conductive component for a number of other bi-metal composites. Together with information on strength properties (taken from previous literature), the conductivity information we provide in this work can help to identify new promising candidate materials (such as Cu/Nb, Cu/Ag, Cu/W, …) for magnet applications with the highest achievable field strengths.

Machine learning assisted search for Fe–Co–C ternary compounds with high magnetic anisotropy

We employ a machine learning (ML)-guided framework to explore rare earth free magnetic materials, specifically focusing on Fe–Co–C ternary compounds for potential use in permanent magnets. Utilizing a specifically trained crystal graph convolutional neural network model, we efficiently screen a vast space of nearly a million substitutional structures to select 620 promising structures for further investigation by first-principles calculation. We predict five low-energy metastable Fe–Co–C compounds with formation energy less than 150 meV/atom above the convex hull. These compounds exhibit high magnetization (Js > 1.0 T) and significant magnetic anisotropy (K1 > 1.0 MJ/m3), making them promising candidates for permanent magnet applications. The phonon calculations indicate these compounds are dynamically stable. Our ML-guided framework demonstrates the utility of rapidly identifying novel materials with tailored magnetic properties.

Clustered ultra-small iron oxide nanoparticles as potential T1/T2 dual–modal magnetic resonance imaging contrast agents and application to tumor model

Many studies have been conducted on the use of ultra-small iron oxide nanoparticles (USIONs) (d < 3 nm) as potential positive magnetic resonance imaging (MRI)-contrast agents (CAs); however, there is dearth of research on clustered USIONs. In this study, nearly monodispersed clustered USIONs were synthesized using a simple two-step one-pot polyol method. First, USIONs (d = 2.7 nm) were synthesized, and clustered USIONs (d = 27.9 nm) were subsequently synthesized through multiple cross-linking of USIONs with poly(acrylic acid-co-maleic acid) (PAAMA) polymers with many -COOH groups. The clustered PAAMA-USIONs exhibited very weak ferromagnetism owing to the magnetic interaction between superparamagnetic USIONs; this was evidenced by their appreciable r1= 3.9 s‒1mM‒1and high r2/r1ratio of 14.6. Their ability to function as a dual-modal T1/T2MRI-CA in T1-weighted MRI was demonstrated when they simultaneously exhibited positive and negative contrasts in T1-weighted MRI of tumor model mice after intravenous injection. They displayed positive contrasts at the kidneys, bladder, heart, and aorta and negative contrasts at the liver and tumor.&#xD.

Review of the research status of practical superconducting materials and their current carrying performance

Abstract Superconducting materials hold great potential in high field magnetic applications compared to traditional conductive materials. At present, practical superconducting materials include low-temperature superconductors such as NbTi and Nb3Sn, hightemperature superconductors such as Bi-2212, Bi-2223, YBCO, iron-based superconductors and MgB2. The development of low-temperature superconducting wires started earlier and has now entered the stage of industrialized production, showing obvious advantages in mechanical properties and cost under low temperature and middle-low magnetic field. However, due to the insufficient intrinsic superconducting performance, low-temperature superconductors are unable to exhibit excellent performance at high temperature or high fields. Further improvement of supercurrent carrying performance mainly depends on the enhancement of pinning ability. Hightemperature superconductors have greater advantages in high temperature and high field, but many of them are still in the stage of further performance improvement. Many high-temperature superconductors are limited by the deficiency in their polycrystalline structure, and further optimization of intergranular connectivity is required. In addition, it is also necessary to further enhance their pinning ability. The numerous successful application instances of high-temperature superconducting wires and tapes also prove their tremendous potential in electric power applications.