Magnetization Curves Research Articles

Superconductivity in Ternary Germanite TaAl x Ge2-x with a C40 chiral structure

Abstract We report a new family of chiral intermetallic superconductors TaAl x Ge2-x . The mother compound TaGe2 has a C40-type chiral hexagonal crystal structure with a pair of enantiomorphic space groups of P6222 and P6422. By substituting Ge with Al, TaAl x Ge2-x polycrystals with the C40 structure were synthesized with Al substitution x from 0 to 0.8. Magnetic susceptibility, magnetization curves and electrical resistivity revealed that TaAl x Ge2-x with x of 0.2 to 0.4 was a type-II superconductor with a superconducting transition temperature T c of 2.0 to 2.2 K. The superconductivity disappeared at with x less than 0.2 or was largely suppressed at with x of 0.5 or more, although all the measurements were performed at temperatures above 1.8 K. An emergence of superconductivity is discussed in terms of the lattice constants changes with the Al substitution.

Magnetothermal effect and first-principles calculations of Zn-doped Mn5Ge3-based alloys

This study investigates the compound system Mn5−xZnxGe3 (x = 0.1, 0.2, and 0.3) through experimental investigations and theoretical calculations. Zn doping lowers the Curie temperature and magnetic entropy change of Mn5−xZnxGe3 alloys. Analysis of phenomenological curves, including Landau theories, normalized curves, and Arrott curves during the study of isothermal magnetization curves, reveals a second-order phase transition in this system. Through an extensive investigation of critical behavior using critical isotherm curves and the Kouvel–Fisher (KF) method, the consistency and reliability of these critical indices are validated by the prediction of the scaling theory in the critical region. By scaling the dependence of |ΔSM| on M and applying crucial exponen21t values, an efficient new approach is utilized to calculate the spontaneous magnetization that agrees well with the values deduced from the KF method. Additionally, first-principles calculations reveal that the Mn atoms' 3d orbitals are more significantly close to the Fermi energy level, with Zn doping generally reducing both the electronic density of states and the total magnetic moment of the Mn 3d orbitals. Consequently, the introduction of Zn leads to a decrease in the Mn–Mn atom exchange coupling, resulting in a deterioration of the total exchange interaction. This phenomenon also explains the decrease in the Curie temperature TC due to Zn doping, aligning with experimental observations.

A Conjugate Linearly Polarized Light Wave Along an Optical Fiber with the Berry Phase Model and Its Magnetic Trajectories According to the Conjugate Frame

In this article, we study how a linear polarized wave that is going along an optical fiber works, which is known not only as a curve on a Lie group but also as a rotation of the polarization plane. What we are trying to show in this article is that linear polarized light waves (PLWs) are related to the Berry phase. Moreover, we give magnetic curves created by N traveling in the electromagnetic trajectories and the optical fiber generated by the electric field N of the PLW moving through the optical fiber. With this described method, we present a mathematical model to conveniently generate the relationships between an optical fiber and the optical angular momentum in a three-dimensional Lie group. The conjugate frame we used in this article removes unnecessary bending around the tangent and enables a more dynamic characterization, which can still be applied even when the second derivative of the curve is zero.

Magnetization Plateaus by the Field-Induced Partitioning of Spin Lattices

To search for a conceptual picture describing the magnetization plateau phenomenon, we surveyed the crystal structures and the spin lattices of those magnets exhibiting plateaus in their magnetization vs. magnetic field curves by probing the three questions: (a) why only certain magnets exhibit magnetization plateaus, (b) why there occur several different types of magnetization plateaus, and (c) what controls the widths of magnetization plateaus. We show that the answers to these questions lie in how the magnets under field absorb Zeeman energy, hence changing their magnetic structures. The magnetic structure of a magnet insulator is commonly described in terms of its spin lattice, which requires the determination of the spin exchanges’ nonnegligible strengths between the magnetic ions. Our work strongly suggests that a magnet under the magnetic field partitions its spin lattice into antiferromagnetic (AFM) or ferrimagnetic fragments by breaking its weak magnetic bonds. Our supposition of the field-induced partitioning of spin lattices into magnetic fragments is supported by the anisotropic magnetization plateaus of Ising magnets and by the highly anisotropic width of the 1/3-magnetization plateau in azurite. The answers to the three questions (a)–(c) emerge naturally by analyzing how these fragments are formed under the magnetic field.

Modeling of partially oriented spring-exchange magnetic composites

PurposeThe presentation refers to simulations of magnetization processes of the spring-exchange magnetic composites containing magnetically soft and ultra-high coercive phases. In particular, the aim of this study is to investigate the possibility of reducing expensive rare earth (RE) in the so-called neodymium magnets and improving their efficiency.Design/methodology/approachIn order to model hysteresis loops, a special disorder-based Monte Carlo procedure, suitable for irregular geometry of the composites, was applied. The chosen system parameters were defined in order to model Nd2Fe14B/Fe composites.FindingsThe results suggest potential for optimizing hard magnetic composites. Magnetization curve parameters are sensitive to grain coupling and easy magnetization axis ordering. Strong coupling for a single-phase hysteresis loop is unachievable for grains above a certain size, i.e. found to be a few hundred nanometers. Considering these factors and their interdependencies, it’s possible to enhance the |BH|max parameter or reduce the RE content.Research limitations/implicationsThe research was carried out using computer simulations, which by their nature are only approximations of physical processes. The next stage of research is to produce the described composites and test their actual properties.Practical implicationsThe research enhances permanent magnets, boosting efficiency in technologies like wind turbines and electric motors, indirectly benefiting the environment. It also reduces RE elements in magnets for environmental, economic and political gains.Originality/valueThe unique approach is to consider the random orientation of the magnetic anisotropy of the hard magnetic grains, which is close to real powder composites. The results provide valuable guidance for the production process of permanent magnets.

A non-newtonian approach to geometric phase through optic fiber via multiplicative quaternions

In this paper, we researched magnetic and electromagnetic curves in multiplicative Euclidean 3-space via multiplicative quaternion algebra. Firstly, we examined the geometric phase representation of the polarized light wave in the optic fiber by multiplicative Frenet frame. Using the quaternionic approaches, we were able to derive the magnetic curve equations and theorems. Then, three particular instances have been illustrated with examples of electromagnetic curves and magnetic field equations. Lastly, we provided an interpretation of the findings. With the help of the results, we were able to present an alternative viewpoint on the construction of trajectories (such as circular or spiral-like ones) that do not exist uniquely in the realm of physics.

Effect of Rare Earth doping on Structural, Morphological, Optical, and Magnetic Properties of the Y1-x(Gd, Dy)xBaCuFeO5+δ (x = 0.2, 0.4, 0.6, and 0.8) Ceramics

The effect of the rare earth (RE) ion substitution on the structural, morphological, optical and magnetic properties of the Y1-xRExBaCuFeO5 (RE = Gd, Dy; x = 0.2, 0.4, 0.6, and 0.8) multiferroic compounds grown by the solid-state reaction is evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), reflectance spectroscopy techniques diffuse (UV-vis-NIR) and vibrating sample magnetometry (VSM). The results indicate that the RE substitution led to growth of single-phase materials, with a tetragonal structure and P4mm symmetry. The morphological analysis shows the formation of polycrystalline materials composed of grains of various shapes and sizes. Furthermore, the compositional analysis reveals that the materials do not present elements other than those used in the synthesis. The band gap (Eg) is tuned from 0.88 to 0.90 eV upon RE substitution. The magnetization curves obtained in the Zero-Field-Cooled/Field-Cooled (ZFC-FC) modes between 50 and 390 K, reveal a paramagnetic behavior, which could be attributed to the dominance exerted by the magnetic moments of the Gd/Dy ions.

Multifunctional hybrid films made from CoT3OTx4 and CoFeT2OT4 nanoparticles inside a poly 3-hydroxybutyrate matrix and study of their impact in methyl orange photodegradation.

This work aims to produce hybrid materials with potential applications in dye photodegradation. Therefore, hybrid films were obtained by incorporating cobalt (II, III) oxide (Co3O4) or cobalt ferrite (CoFe2O4) nanoparticles (NPs) with 18 ± 1.6 nm and 26 ± 1.3 nm, respectively, into a poly 3-hydroxybutyrate (P3HB) polymeric matrix. The Co3O4@P3HB and CoFe2O4@P3HB hybrid films were fabricated by solvent casting in a ratio of 85 mg to 15 mg (P3HB-NPs). Different spectroscopic and microscopy techniques characterized the Co3O4 and CoFe2O4 NPs and the P3HB, Co3O4@P3HB and CoFe2O4@P3HB films. The optical band gap for Co3O4 and CoFe2O4 NPs was estimated from their diffuse reflectance spectra (DRS) around 2.5 eV. X-ray diffraction (XRD) of the hybrid films revealed that the nanometric sizes of the Co3O4 and CoFe2O4 nanoparticles incorporated into the P3HB are preserved. The magnetic hysteresis curve of CoFe2O4 nanoparticles and CoFe2O4@P3HB film showed a ferromagnetic behaviour at 300 K. Transmission electron microscopy (TEM) confirmed the formation of nanocrystals, and scanning electron microscopy (SEM) provided evidence for the successful incorporation of the NPs into the P3HB matrix. The surface roughness and hydrophilicity of the hybrid films are increased compared to the P3HB film. The impact of the nanoparticles and the hybrid films on the photodegradation of methyl orange (MO) in its acidic form was studied. The photodegradation tests were carried out by direct sunlight exposure. The CoFe2O4@P3HB hybrid film achieved 85% photodegradation efficiency of a methyl orange solution of 20 ppm after 15 minutes of exposure to sunlight. After 30 minutes of exposure to sunlight, the nanoparticles and the hybrid films reached about 90% of the MO degradation. The results suggest that combining nanoparticles with the polymer significantly enhances photodegradation compared to isolated nanoparticles.

Cu-doped nanocomposite Pr2Fe14B/α-Fe ribbons with high (BH)max

Abstract The melt-spun ribbons of nominal composition Pr9Fe84.2-xB6.2P0.3Zr0.3Cux (x=0, 0.5, 1, 2) were prepared at wheel speeds of 21, 27, 30, and 33 ms-1. The XRD patterns show that as the wheel speed increases, the crystallinity of the 2:14:1 hard phase decreases, while that of the α-Fe soft phase increases. The (BH)max, remanence, and coercivity are improved from 63 kJm-3, 0.85 T, and 515 kAm-1 for the Cu-free ribbons to 171 kJm-3, 1.08 T, and 684 kAm-1 with x=0.5. The high squareness ratio of Jr/Js ~ 0.82 at 0.5 at. % Cu (27 ms-1) indicates strong exchange coupling due to small grain sizes of 15 and 30 nm for soft and hard magnetic phases, respectively. The SEM images revealed smooth morphology and uniform element distribution at 0.5 at. % Cu (27 ms-1), contributing to the high magnetic properties. The low recoil permeability (μ rec ) value of 5.466×10-4 to 1.970×10-4 $\frac{T}{k A m^{-1}}$ confirms the strong exchange coupling with x=0.5 (27 ms-1). The initial magnetization curves show that the coercivity mechanism of the Cu-free alloy evolves from the nucleation of the reverse domain to the domain wall pinning as the wheel speed increases, resulting in a high coercivity value of 818 kAm-1 (33 ms-1). Conversely, for the Cuadded alloy, the coercivity mechanism changes from pinning to the nucleation of the reverse domain from low to high wheel speed.

Strong Antiferromagnetic Interactions in the Binuclear Cobalt(II) Complex with a Bridged Nitroxide Diradical

A binuclear cobalt–radical complex formed by the reaction of Co(hfac)2·2H2O (hfac = hexafluoroacetylacetonate) with the 2,2-bis(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolinyl) biradical (BR) has been synthesized. The complex {(hfac)CoII(BN)CoII(hfac)} crystallizes in the triclinic space group P1¯ : C34H28Co2F24N4O12, a = 11.1513(5) Å, b = 12.8362(7) Å, c = 18.2903(8) Å, α = 103.061(1)°, β = 100.898(2)°, γ = 102.250(1)°, Z = 2. The compound consists of two non-equivalent pseudo-octahedral CoII ions, each bearing two hfac ancillary ligands bridged by the tetradentate bis-nitroxide (BN). The temperature dependence of the magnetic susceptibility indicates a strong antiferromagnetic exchange between each of the Co2+ ions and the nitroxyl biradical, as well as between the spins within the bridging ligand, forming a spin-frustrated system. Micro-squid investigations, performed on a single crystal of {(hfac)CoII(BN)CoII(hfac)}, reveal a peculiarity of the M(H) graph at temperatures below 0.4 K displaying a step that is a result of ground and first excited levels mixing by the applied magnetic field due to a small energy gap between them, as inferred from ab initio calculation. The latter was also carried out for two models of mononuclear Co2+ complexes in order to obtain a set of initial parameters for fitting the experimental magnetic curves using the Phi program. Moreover, direct CAS(12,10)/def2-TZVP calculations of the magnetic dependences χT(T) and M(H) were performed, which satisfactorily reproduced the experimental ones.

Hysteresis in seasonal land-atmospheric interactions over India and its characteristics across croplands and forests

Abstract Satellite-derived Vegetation Optical Depth and Soil Moisture (SM) data reveal the critical role of the soil-vegetation continuum in storing rainwater during the Indian Summer Monsoon and supporting evapotranspiration (ET) during the dry non-monsoon season. During the non-monsoon drier period, the climatologically estimated spatial mean of ET exceeds precipitation input, a phenomenon known as the Soil-Vegetation Capacitor (SVC) effect, which is pivotal in maintaining ecosystem productivity. Notably, our analysis reveals significant variations in the capacitor period between croplands and forests, with croplands exhibiting a ~77 days longer due to dual crop seasons influenced by regional precipitation. The well-recognized hysteresis curves, observed in magnetization and soil-water characteristic curves (SWCC), highlight phenomena where a system's state is influenced by its historical inputs or states and are integral to our findings. We report a previously undocumented seasonal hysteresis in the relationship between the evaporative fraction (EVF) and SM for Indian croplands and forests. We further found that the croplands SM-EVF relation exhibits a reversal in hysteresis in the case of root-zone SM. The surface SM-EVF hysteresis is not present in forests with large root depths and reduced soil evaporation due to high canopy shading, and yet it is present for the root-zone SM. With its reversal for croplands, the newly found hysteresis must be addressed in redefining the critical SM threshold to demarcate the energy and water-limiting regimes. It should be incorporated in the land surface modeling parameterization. Additionally, we observed hysteresis in the soil moisture-gross primary productivity (SM-GPP) relationship across both land covers and soil profiles (surface and root-zone), underscoring the need to investigate such processes to consider their dynamics in future ecological and hydrological models.

Simple extraction method of magnetic hysteresis curve from measurement data

Simple extraction method of magnetic hysteresis curve from measurement data

Investigation of annealing temperature effect on structural, morphological, optical, magnetic, and dielectric properties of cobalt-doped manganese ferrites

Spinel ferrite Mn0.95Co0.05Fe2O4 was prepared via chemical co-precipitation routes and annealed at four distinct temperatures of 600 °C, 650 °C, 700 °C, and 750 °C. The XRD peak confirmed a single-phase cubic spinel structure, with an increasing crystallite size of 21.64–23.98 nm by the annealing effect. The TEM images show an increase in particle size with rising annealing temperature and indicate well-defined nanocrystalline Mn-Co ferrite. FT-IR spectra detected two vibrational modes at interstitial sub-lattice sites, identifying Co-O, Mn-O, and Fe-O bonds with the spinel structure of Mn-Co ferrite. UV–vis–NIR reflectance revealed an optimal direct band gap of 3.76–4.70 eV, indicating a scope of semiconducting behaviors in the nanocatalysts. In the magnetic hysteresis curve, saturation magnetization decreased while coercivity increased with rising annealing and crystallite size. The M-T loop reveals the Curie temperature of Mn-Co ferrite decreases from 533.84 °C to 382.74 °C. Frequency-dependent complex permeability at different annealing temperatures shows stable initial permeability over a wide frequency range (1 kHz to 100 MHz) and a quality factor several times higher due to reduced magnetic tangent loss. The real dielectric constant and losses decline in rising alternating fields (100 Hz to 1 MHz) and stabilize at higher frequencies following Maxwell-Wagner-type polarization. Eventually, structural, morphological, and magnetic properties are performed relatively well at higher annealing temperatures, and optical and dielectric properties are performed at lower annealing temperatures.

Banana fruit (Musa sp.) DNA-magnetite nanoparticles: Synthesis, characterization, and biocompatibility assays on normal and cancerous cells.

Magnet-mediated gene therapy has gained considerable interest from researchers as a novel alternative for treating genetic disorders, particularly through the use of superparamagnetic iron oxide nanoparticles (NPs)-such as magnetite NPs (Fe3O4NPs)-as non-viral genetic vectors. Despite their commercial availability for specific genetic transfection, such as in microglia cell lines, many potential uses remain unexplored. Still, ethical concerns surrounding the use of human DNA often impede genetic research. Hence, this study examined DNA-coated Fe3O4NPs (DNA-Fe₃O₄NPs) as potential transfection vectors for human foreskin fibroblasts (HFFs) and A549 (lung cancer) cell lines, using banana (Musa sp.) as a low-cost, and bioethically unproblematic DNA source. Following coprecipitation synthesis, DNA-Fe₃O₄NP characterization revealed a ζ-potential of 40.65 ± 4.10 mV, indicating good colloidal stability in aqueous media, as well as a superparamagnetic regime, evidenced by the absence of hysteresis in their magnetization curves. Successful DNA coating on the NPs was confirmed through infrared spectra and surface analysis results, while magnetite content was verified via characteristic X-ray diffraction peaks. Transmission electron microscopy (TEM) determined the average size of the DNA-Fe3O4NPs to be 14.69 ± 5.22 nm. TEM micrographs also showed no morphological changes in the DNA-Fe3O4NPs over a 30-day period. Confocal microscopy of HFF and A549 lung cancer cell lines incubated with fluoresceinamine-labeled DNA-Fe3O4NPs demonstrated their internalization into both the cytoplasm and nucleus. Neither uncoated Fe3O4NPs nor DNA-Fe3O4NPs showed cytotoxicity to A549 lung cancer cells at 1-50 μg/mL and 25-100 μg/mL, respectively, after 24 h. HFFs also maintained viability at 1-10 μg/mL for both NP types. In conclusion, DNA-Fe3O4NPs were successfully internalized into cells and exhibited no cytotoxicity in both healthy and cancerous cells across a range of concentrations. These NPs, capable of binding to various types of DNA and RNA, hold promise for applications in gene therapy.

Tunnel magnetoresistive sensors with non-hysteretic resistance–magnetic field curves using noncollinear interlayer exchange coupling through RuFe spacers

Tunnel magnetoresistive sensors with non-hysteretic resistance–magnetic field curves using noncollinear interlayer exchange coupling through RuFe spacers

Optically Responsive Hydrogel with Rapid Deformation for Motion Regulation of Magnetic Actuators.

Optically and magnetically responsive soft actuators are gaining attention for their noncontact actuation, flexibility, and remote control capabilities. However, they face challenges in rapidly switching motion postures and modes, which limits their performance in complex environments. We developed bilayer hydrogel actuators based on poly(N-isopropylacrylamide) (PNIPAm) using an ice-templating method combined with free radical polymerization. This approach results in the formation of large, interconnected pores within the hydrogel. Under near-infrared light (27 W/cm2), the actuation speed of the actuator reached 38.5°/s, with complete recovery to the original shape 8 s after light cessation. In addition, the reversible changes in stiffness and volume enable the actuators to lock and dynamically adjust their magnetization curve, allowing for the decoupling of deformation and movement as well as the regulation of motion postures and modes. This work opens new pathways for multigait robots and shows promising applications in environmental monitoring and underwater exploration.

Magnetization Processes of Exchange Coupled Nd2(Fe,Co)14B Alloys in Various Demagnetized States

Processes of magnetization in exchange-coupled rapidly quenched nanocrystalline alloys Nd2(Fe1-xCox)14B, where x = 0, 0.07, 0.2, 0.5, have been studied. Initial magnetization curves and interaction plots δM(H) for various demagnetized states were obtained. Based on comparison of measurement results, influence of the pinning type mechanism on magnetization process in the Nd2(Fe1-xCox)14B melt-spun ribbons is shown. Using δM(H) plots, change in intergrain exchange interaction depending on cobalt concentration in rapidly quenched Nd2(Fe1-xCox)14B nanocrystalline alloys was investigated.

Thermal hysteresis in Ho thin films − experimental results and modeling

This paper presents the results of theoretical modeling and experimental studies of thermal hysteresis in holmium (Ho) thin films with a thickness of 200 nm at applied magnetic fields of 100 Oe, 1 kOe, and 10 kOe. The isofield magnetization curves, measured at 100 Oe and 1 kOe do not exhibit hysteresis during the heating and cooling processes. In contrast, M(T) measured at 10 kOe shows significant differences between the heating and cooling processes. The thermal hysteresis width covers almost the entire range between the Curie temperature (TC) and Néel temperature (TN) and is controlled by the external magnetic field. The peculiarities of the magnetic phase diagram of thin films in comparison with the bulk samples of Ho are also discussed.

Effect of salinity-clay variation on the transient magnetic field in the Quaternary aquifer, theoretically and practically

This study focuses on understanding the physical foundations of the transient electromagnetic method, such as the transition from a simple basic principle to a more complex principle, starting from the Biot-Savart law until the current concept. It calculates the steady and transient magnetic fields around any electrical wire system. Accordingly, this law will be used to determine the magnetic field around the square loop configuration, which matches the magnetic field arising from the circular loop configuration. The square loop equation was derived and extended to include changes in the half-space, which allows us to understand how the electromagnetic waves travel in the subsurface and the farthest point, that can record the TEM response from the TEM loop, according to the loop size and loop current. Accordingly, the deduced equations were applied to predict the transient magnetic field curves of the Quaternary aquifer in three different water zones along the Nile delta, depending on the values of resistivity and chargeability caused by the variations in salinity and clay contents. The calculated transient magnetic curves were then compared with other measured field curves to confirm the validity of the derived equations. Therefore, these curves are expected to be used as guide curves for the transient magnetic field response in this aquifer. Also, these curves are important in estimating the hydro-geophysical characteristics of the main groundwater aquifer in the selected area and in other areas with the same geologic and hydrogeologic settings. Also, a common model is presented for any delta environment in the world in measured and calculated data.

Magnetic field-enhanced two-electron oxygen reduction reaction using CeMnCo nanoparticles supported on different carbonaceous matrices

The current study illustrates the successful synthesis of Ce1.0Mn0.9Co0.1 nanoparticles, characterized through XRD, EPR, magnetization curves, and TEM/HRTEM/EDX analyses. These nanoparticles were then loaded into the carbon Vulcan XC72 and the carbon Printex L6 matrices in varying amounts (1, 3, 5, and 10 % w/w) via wet impregnation method to fabricate electrocatalysts for the 2-electron ORR. Before experimentation, the material was characterized via XPS and contact angle measurements. The electrochemical results produced significant findings, indicating that the electrocatalysts with the nanostructures modifying both carbon blacks notably augmented currents in rotating ring-disk electrode measurements, signifying enhanced selectivity for H2O2 production. Moreover, our research underscored the significant impact of Magnetic Field-Enhanced Electrochemistry, employing a constant magnetic field strength of 2000 Oe, on 2-electron ORR experiments. Particularly noteworthy were the observed results surpassing the ones without the magnetic field, demonstrating heightened currents and improved selectivity for H2O2 production (more than 90 %) facilitated by CeMnCo nanoparticles. These significant findings in electrocatalytic efficiency have practical implications, suggesting the potential for developing more efficient and selective catalysts for the 2-electron ORR.