Magnetic Nature Research Articles

Confirmation of two magnetic cataclysmic variables as polars: 1RXS J174320.1−042953 and YY Sex

ABSTRACTWe present our analysis of new and archived observations of two candidate magnetic cataclysmic variables, namely 1RXS J174320.1−042953 and YY Sex. 1RXS J174320.1−042953 was observed in two distinctive high and low states where a phase shift was seen, which could be due to changes in the shape, size, and (or) location of the accretion region. We find that its orbital X-ray modulations only persist in the soft (0.3–2.0 keV) energy band, which could be attributed to photoelectric absorption in the accretion flow. The X-ray spectra exhibit a multi-temperature post-shock region where the hard X-rays are absorbed through a thick absorber with an equivalent hydrogen column of ∼7.5 × 1023 cm−2, which partially covers ∼56 per cent of the emission. No soft X-ray excess was found to be present; however, a soft X-ray emission with a blackbody temperature of ∼97 eV describes the spectra. Extensive Transiting Exoplanet Survey Satellite (TESS) observations of YY Sex allow us to refine its orbital period to 1.5746 ± 0.0011 h. We did not find any signature of previously reported spin or beat periods in this system. Furthermore, our new polarimetric observations show clear circular polarization modulated on the orbital period only. Finally, both systems show strong Balmer and He ii 4686 Å emission lines in the optical spectra, further indicative of their magnetic nature.

Planarization of negatively curved [7]circulene on a graphene monolayer

[7]Circulene (C28H14) is the smallest saddle-shaped [n]circulene with negative Gaussian curvature. The electronic properties of highly curved π-systems change upon planarization, and therefore the induced planarization of these systems has attracted considerable attention in recent years. Here we use dispersion-corrected density functional theory (DFT) calculations (at the PW6B95-D4/def2-QZVP level) to show that the highly nonplanar [7]circulene adopts a completely planar equilibrium structure upon adsorption on a nanographene (modeled as C96H24). This planarization is rooted in strong dispersion and electrostatic interactions between the [7]circulene and C96H24 (est. as △Ee,int = 166.9 kJ mol−1), which are significantly stronger than the planarization energy of the free [7]circulene (est. as △Ee,planar = 40.0 kJ mol−1). Upon planarization, the magnetic nature of [7]circulene changes from nonaromatic to antiaromatic. Thus, this graphene-induced planarization provides a novel approach for a reversible nonaromatic/antiaromatic molecular switch.

Large Orbital Magnetic Moment in VI3.

The existence of the V3+-ion orbital moment is an open issue of the nature of magnetism in the van der Waals ferromagnet VI3. The huge magnetocrystalline anisotropy in conjunction with the significantly reduced ordered magnetic moment compared to the spin-only value provides strong but indirect evidence of a large V orbital moment. We used the unique capability of X-ray magnetic circular dichroism to determine the orbital component of the total magnetic moment and provide a direct proof of an exceptionally sizable orbital moment of the V3+ ion in VI3. Our ligand field multiplet simulations of the XMCD spectra in synergy with the results of DFT calculations agree with the existence of two V sites with different orbital occupations and OM magnitudes in the ground state.

Review on structural, magnetic, optical properties of manganese doped zinc oxide nanoparticles

Due to its distinctive features and potential applications, the ZnO nanostructure has received extensive attention in recent years. The addition of a transition metal allows ZnO optical and magnetic characteristics to be tuned, which enhances the applicability. Mn doped ZnO has received the significant attention among all transition metals due to notable improvement in ZnO magnetic behaviour at ambient temperature. The magnetism in ZnO is quite controversial and still needs a proper justification, but substitution of magnetic ions undoubtedly enhances the magnetic nature of ZnO. In this review, we have summarised the properties and applications of ZnO and explored the possible mechanism to enhance its property to make it more applicable. Overviews of the ZnO synthesis procedure, uses, and dopant impacts on the structural, magnetic, and optical characteristics of ZnO nanoparticles are provided in this work. The effect of Mn doping concentration on both magnetic and optical behaviour is assessed and justified appropriately. This work will help the novice researcher to observe the applicability of Mn doped ZnO for optoelectronic devices.

Magnetic, dielectric and electrical modulus of Ce3+ doped cobalt–magnesium ferrite nanoparticles

In this work, the magnetic, dielectric properties and electric modulus of Ce3+ substituted cobalt-magnesium (Co0.7Mg0.3CexFe2–xO4) (labeled as CMCF) ferrite nanoparticles were investigated in detail. Saturation magnetization decreases from 50.05 to 34.87 emu/g for further substituting Ce3+ ions. Meanwhile, coercivity increases from 738.22 Gs for the CMCF0 sample to 912.10 Gs for the CMCF2 sample, then decreases monotonically to 762.1 Gs for the CMCF5 sample. The cerium content and particle size play important roles in controlling the magnetization and coercivity of the CMCF nanoparticles. All CMCF nanoferrites are suitable for microwave applications since their high-frequency response ranges from 7.72 to 11.07 GHz. The CMCF nanoferrites' dielectric parameter dispersion exhibits normal behavior. The pristine Co–Mg nanoferrite only has ε′ value of 28.25, but the nanoferrite MCMF2 has ε′ value of 365.03, with an enhancing ratio of 1192%. The conduction mechanism of the MCMF nanoferrites was determined by fitting the σac results via the Jonscher power law. At 653 K, large polaron tunnelling is thought to be responsible for this conduction process, which is followed by electron barrier hopping at higher temperatures. Cole–Cole diagrams at different temperatures, assuring the contributions of the grains and their boundaries at lower temperatures (653 K) and only the grains at higher temperatures. Based on our results, the CMCF nanoferrites hold magnetic and semiconducting nature, which can be used in magnetic devices and dielectrics in lower-frequencies or conductors in higher-frequencies.

Investigation of calcium substitution on magnetic and dielectric properties of Mg–Zn nano ferrites

In this work, an efficient, cost-effective, and less time-consuming citrate precursor wet chemical approach was employed to prepare a series of Calcium (Ca) doped Magnesium–Zinc ferrite of composition Mg0.4Zn0.6-xCax Fe2O4 (0.0 ≤ x ≤ 0.6). X-ray diffraction (XRD), Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) analysis confirmed the spinel structure and nanometric size of the particles. Williamson-Hall (W–H) plots were drawn by making use of XRD data and calculated values of lattice strain were found in the range (3.00 × 10−3 to 9.09 × 10−3) for various concentrations of calcium. The cubic spinel structure of produced ferrites was also verified by three active Raman modes (A1g, Eg, and T2g). In the Vibrating sample magnetometer (VSM) study, an “S” shape curve shows the low values of coercivity for all the samples in the range 59–105 Oe. For all Ca concentrations, the dielectric loss tangent values were evaluated to be extremely low 0.03 to 0.18 at 1 MHz frequency. The highly magnetic nature and very low value of loss factor make this prepared nanoferrite material best suited for the manufacturing of high-frequency application devices.

The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane‐Derived Silicon Oxycarbide

A facile and novel processable method to synthesize the Ni nanoparticles (Ni NPs) by tailoring their size in the matrix of the silicon oxycarbide (SiOC) ceramic system is reported. This method is based on polymer‐derived ceramics (PDCs), instead of the conventional powder route. The specific structural characteristics and magnetic properties of the various Ni NPs/SiOC composites as a function of carbon content are systematically investigated. The magnetic properties are experimentally investigated as a function of NP size and measurement temperature. It is demonstrated that the change in the size of Ni NPs (average from ≈4 to ≈ 19 nm) determines the magnetic nature of superparamagnetism. Zero‐field‐cooled (ZFC) and field‐cooled (FC) magnetization studies under magnetic fields of 100 Oe are performed. The saturated M versus H (M–H) loops (saturation magnetization) increase and the coercivity decreases with the size reduction of Ni NPs. It is an indicator of the presence of superparamagnetic behavior and single‐domain NP for ceramic materials.

A Theoretical Account of the Coupling between Metal- and Ligand-centred Spins.

This study addresses the magnetic interaction between paramagnetic metal ions and the radical ligands taking the [CuII (hfac)2 (imVDZ)] and [MII (hfac)2 (pyDTDA)] (imVDZ=1,5-dimethyl-3-(1-methyl-2-imidazolyl)-6-oxoverdazyl; hfac=(1,1,1,5,5,5)hexafluroacetylacetonate; pyDTDA=4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl), (M=Cu, Ni, Co, Fe, Mn) compounds as reference systems. The coupling between the metal and ligand spins is quantified in terms of the exchange coupling constant (J) in the platform of density functional theory (DFT) and the wave function-based complete active space self-consistent field (CASSCF) method. Application of DFT and broken symmetry (BS) formalism results ferromagnetic coupling for all the transition metal complexes except the Mn(II) complex. This DFT-BS prediction of magnetic nature matches with the experimental finding for all the complexes other than the Fe(II)-pyDTDA complex, for which an antiferromagnetic coupling between high spin iron and the thiazyl ligand has been reported. However, evaluation of spin state energetics through the multiconfigurational wave function-based method produces the S=3/2 ground spin state for the iron-thiazyl in parity with experiment. Electronic structure analyses find the overlap between the metal- and ligand-based singly occupied molecular orbitals (SOMOs) to be one of the major reasons attributing to different extent of exchange coupling in the systems under investigation.

Interplay of dopant and polarons in trifunctional semimagnetic semiconductor for supercapacitor applications: Local structure and electronic structure investigations

Diluted magnetic semiconductors (DMS), fractionally doped by magnetic ions, are peculiar, and a single semiconductor effectively contributes to charge and spin properties for various applications, including data and energy storage. Here, a low temperature assisted co-precipitation method produced a series of Co doped ZnO nanoparticles. After structural characterizations, zinc vacancy defects were realized via the hyperfine signal with g ∼ 1.96 (spin resonance) and the emissions (photoluminescence) at 410 and 465 nm. The synergistic effect among the Co dopant, native, and polaron defects makes the system exhibit enhanced polarization and electrochemical reactions. Magnetization hysteresis curves demonstrate the intrinsic magnetic nature of the materials that are essential for realizing useful polaronic states. As an anode material, 20 at. % Co doped electrode has a higher specific capacitance and superior cycling stability with charge retention above 98 %, which is much higher than the other ZnO-based electrodes and is associated with the polaron-assisted rapid redox reactions. These polarons also stimulate a ferroelectric polarization of 0.28 μC cm−2 via local lattice distortion. All these findings confirm that the Co doped semi-magnetic ZnO system with multifunctionality is adequate for employment in device fabrication as a low-cost, highly stable material.

Improvement of cavitation erosion resistance of structural metals by alternating magnetic field treatment

Results of cavitation erosion tests for EN8 steel, nickel-aluminium bronze (NAB), 70/30 brass and aluminium alloy AA2014-T6 following alternating magnetic field (AMF) treatment are presented. These alloys were selected because of their magnetic nature; EN8 steel is ferromagnetic, NAB and 70/30 brass are diamagnetic and AA2014 alloy is paramagnetic. The indirect cavitation erosion tests (ASTM G32–10 standard) were fulfilled at a frequency of 20 kHz in deionized water which was maintained at room temperature and ambient pressure for a predetermined time. The results show significant decrease in the mass loss for all samples that had underg1 AMF treatment. The eroded samples were characterised by means of scanning electron microscopy, while microhardness measurements showed an increase in the surface hardness as a result of the AFM treatment. The results of X-ray diffraction indicated formation of more compressive residual stresses following treatment, while examination by transmission electron microscopy showed evidence of dislocation movement away from grain boundaries. In the case of the NAB and 20014-T6 alloys, there was evidence of new precipitation. By considering the deformed state and the magnetic nature of each alloy, mechanisms explaining the increase in the cavitation erosion resistance due to the treatment are proposed and discussed.

Magnetic drug targeting during Casson blood flow in a microvessel: A Caputo fractional model

A mathematical model on fractionalized axisymmetric Casson blood flow through a cylindrical shaped blood vessel is introduced to present the capture location of drug carrier particles at diseased regions during magnetic drug targeting (MDT). The Caputo fractional order time-derivative is introduced in the momentum equation to impose the time memory effect. The governing momentum equation is solved analytically in terms of Lorenzo – Hartley and Robotonov – Hartley special functions using Laplace transform (LT) and finite Hankel transform (FHT). The outcome solution for coupled force balance equations is solved using fourth order Runge – Kutta (RK) method, whereas the total volume fraction (TVF) of magnetic nanoparticles (MNPs) is obtained analytically. The present model introduced the effects of magnetic parameter, Darcy number, Reynolds number and pulsatile frequency with the impact of the memory effect in the form of the fractional parameters on the axial and radial trajectories of drug carrier particles (CPs) and on the volume fraction of MNPs. The impacts of tumor-magnet distance, Casson parameter, and Hematocrit parameter on the volume fraction of MNPs is also investigated. A comparison is made with the existing literature, and it shows a good agreement. Short time memory effect leads to a speedy move of the drug particles towards the disease region and the phenomenon is more significant with increase in the volume fraction of the MNPs, magnetization and permeable nature of the microvessel. The outcome of the present study will be helpful to the field of medical science to carry out further research to treat disease in specific locations by using MDT.

First-principles prediction of 1H-Na2Se monolayer: effects of external strain and point defects associated with constituent atoms

In this work, a new Na2Se monolayer in 1H-phase, with interesting properties similar to transition metal dichalcogenides (TMDs), has been predicted using first-principles calculations. Results reveal good stability and wide direct gap semiconductor nature, with an energy gap of 0.82(1.45) eV as determined by standard PBE(hybrid HSE06) functional. This two-dimensional (2D) material exhibits poor stability under compressive strain due to the sensitive ZA acoustic phonon mode. In contrast, it only becomes unstable with tensile strain from 9% due to the elongation of chemical bonds reflected in the optical E” phonon mode. Under effects of lattice tension, the direct gap character is preserved and the band gap increases nearly linearly according to increase the strain strength. In addition, the effects of point defects associated with Na and Se atoms, including vacancies, antisites, and atom adsorption are also examined. Results indicate significant magnetization induced by Na single vacancy, Se Na antisite (one Na atom substituted by one Se atom), and Na adsorption on-top of hollow (T H ) site. In these cases, feature-rich magneto-electronic properties as half-metallic and magnetic semiconductor natures are obtained. In contrast, the formation of 2Na+1Se combined vacancies as well as other defects related to Se atoms leads to an effective band gap modification, even metallization in some cases. Results introduces new promising 2D material for optoelectronic applications and proposes point defect engineering to create artificially novel features for spintronic applications.

Tailoring the magnetic landscape in Al-doped LaMnO3: an experimental and computational perspective

We have reported the synthesis, structural and magnetic properties of LaAl x Mn1−x O3 (x = 0.05, 0.15, 0.25) in this article. We have synthesized these compounds through the Sol-gel citrate method and performed the Rietveld refinement of X-ray diffraction data to determine the lattice parameters. The surface elemental composition and oxidation states of LaAl0.25Mn0.75O3 are investigated using X-ray photoelectron spectroscopy (XPS) in a wide energy window of 0–1200 eV. The magnetic study shows the ferromagnetic transition of these materials. To understand the nature of magnetization from the experiments, we have studied the first principle density functional theory (DFT) and Monte-Carlo simulation. From the DFT calculations, we have confirmed the ferromagnetic structure in the ground state and studied the electronic structure of these materials. The Monte Carlo simulation has been done through the anisotropic Ising model to analyze the origin of magnetic phase transition. We have determined the anisotropy and the interaction constants from the DFT calculations. The double exchange interaction is mainly responsible for the ferromagnetic ground state.

Removal of pharmaceuticals from aqueous medium by alginate/polypyrrole/ZnFe2O4 beads via magnetic field enhanced adsorption

The physicochemical and structural characteristics of the magnetic materials can be modulable due to exposition to a magnetic field, which allows, for example, to enhance its adsorption performance. In this sense, this study describes the preparation of magnetic beads of alginate/polypyrrole/ZnFe2O4 (Alg/PPy/ZnFe2O4) and investigates the effect of an external magnetic field (EMF) on their adsorption performance towards two overconsumed drugs, acetaminophen (ACT) and ibuprofen (IBU). Characterization analyses confirmed the composite formation and magnetic nature of Alg/PPy/ZnFe2O4. Conversely to the pristine beads (Alg/PPy), the presence of an EMF altered the swelling and pHPZC behavior of the magnetic beads, indicating that these properties are affected by this external stimulus. Batch experiments revealed that the amount of ACT and IBU adsorbed by Alg/PPy/ZnFe2O4 in 60–70 min is appreciably high (106.7 ad 108.2 mg/g). The presence of an EMF modulated the structure of Alg/PPy/ZnFe2O4 beads enhancing their adsorption capacity towards ACT and IBU by 14% and 12% compared to Alg/PPy. Kinetic analysis revealed that the adsorption of both drugs on Alg/PPy/ZnFe2O4 followed a pseudo-second-order. Besides, the adsorption mechanism was fitted by the Freundlich isotherm. Reuse experiments showed that the magnetic beads keep a high adsorption capacity for both drugs even after ten consecutive reuse cycles. The results presented here suggest that magnetic-responsive materials like Alg/PPy/ZnFe2O4 are prominent and modulable tools for improving the treatment of water/wastewater containing this class of contaminants.

A magnetic nano-sorbent incorporating antimicrobial papain for the rapid and efficient removal of levofloxacin and Pb(ii) from aqueous systems

In the contemporary century, bio-based magnetic nanomaterials have received tremendous interest as promising candidates in adsorption procedures owing to their magnetic nature, modifiability, approachability, bioactivity, and pH-responsive dynamics.

Functionalization of an ionic honeycomb KF monolayer via doping.

Doping has been widely employed to functionalize two-dimensional (2D) materials because of its effectiveness and simplicity. In this work, the electronic and magnetic properties of pristine and doped KF monolayers are investigated using first-principles calculations based on density functional theory (DFT). Phonon dispersion curves and ab initio molecular dynamics (AIMD) snapshots indicate good stability of the pristine material. The band structure shows an insulating behavior of the KF monolayer, with indirect gaps of 4.80 (6.53) eV as determined using the PBE (HSE06) functional. Its ionic character is also confirmed by the valence charge distribution and Bader charge analysis, and is generated by charge transfer from the K-4s orbital to the F-2p orbital. Doping at both anion and cation sites is explored using N/O and Ca/Sr as dopants, respectively, due to their dissimilar valence electronic configuration in comparison with that of the host atoms. It is found that the KF monolayer is significantly magnetized, where total magnetic moments of 2.00 and 1.00 μB are obtained via N and O/Ca/Sr doping, respectively. Moreover, the appearance of new middle-gap energy states leads to the development of a magnetic semiconductor nature, which is regulated by N-2p, O-2p, Ca-3d, Ca-4s, Sr-4d, and Sr-5s orbitals. Further investigation of codoping indicates that a magnetic-semiconductor nature is preserved, where the synergistic effects of dopants play a key role in the electronic and magnetic properties of the codoped systems. The results presented herein introduce doping as an efficient approach to functionalize the ionic KF monolayer to obtain prospective d0 spintronic materials, a functionality that is not accounted for by the pristine monolayer.

TWO-DIMENSIONAL MODELING OF MAGNETIC ANOMALY DATA REDUCED TO THE POLES IN THE ANDESITIC PROSPECT AREA OF THE SOUTHEAST SLOPE OF SLAMET VOLCANO, INDONESIA

Reduction to the pole (RTP) is a magnetic anomaly data processing filter to remove the influence of the magnetic inclination angle. This filter is needed because of the magnetic dipole nature which complicates the interpretation process. The research aims to explore andesite rocks through the application of RTP to the local magnetic anomalies data in Kutasari District, Purbalingga Regency, Indonesia. The research procedures include data acquisition, processing, modeling, and interpretation. The 2D-modeling results on the local magnetic anomalies data have produced three layers of rock. Layer with a susceptibility value of 0.00291 cgs is interpreted as vesicular andesitic rocks, layer with a susceptibility value of 0.02307 cgs is interpreted as massive andesitic rocks, meanwhile layer with a susceptibility value of 0.00721 cgs is interpreted as undifferentiated volcanic rocks. The results showed that the west to northwest part of the study area is the most prospective area containing andesite rocks.

Doping-mediated electronic and magnetic properties of graphene-like ionic NaX (X = F and Cl) monolayers.

In this work, the stability, and electronic and magnetic properties of pristine and doped graphene-like ionic NaX (X = F and Cl) monolayers are explored using first-principles calculations. The good stability of NaF and NaCl monolayers is confirmed by phonon dispersion curves and ab initio molecular dynamics simulations. Electronic structure calculations show their insulator nature with large indirect band gaps of 5.43 (7.26) and 5.06 (6.32) eV as calculated with the PBE (HSE06) functional, respectively. In addition, their ionic character is also demonstrated. Furthermore, a doping approach is explored to functionalize NaX monolayers for spintronic applications. For such a goal, IIA- and VIA-group atoms are selected as dopants due to their dissimilar valence electronic configuration as compared with the host atoms. The results indicate the emergence of magnetic semiconductor nature with a total magnetic moment of 1μB. Herein, magnetic properties are produced mainly by the dopant atoms, which induce new middle-gap energy states around the Fermi level. Finally, the effects of codoping the NaF monolayer with Ca and O and NaCl with Ba and O are also examined. Adjacent Ca-O and Ba-O pairs preserve the non-magnetic nature. Further separating dopants leads to the emergence of magnetic semiconductor behavior, with lower magnetization than separate doping. This work introduces new ionic 2D materials for optoelectronic and spintronic applications, contributing to the research effort to find out new 2D multifunctional materials.

SYNTHESIS, CHARACTERIZATION, AND INVESTIGATION OF ELECTRICAL, MAGNETIC, SENSOR, AND MECHANICAL PROPERTIES OF POLYANILINE/ZINC DIOXIDE NANOCOMPOSITES

Polyaniline/Nanocomposites were synthesized by the In-Situ Polymerization method. Characterization techniques are used to study the Crystalline nature, Particle size with X-Ray Diffraction, and Chemical composition and bonding by FTIR. Electrical properties were studied by using Keithley 6514 meter to know the conductivity of Polyaniline and Polyaniline / ZnO nanocomposites with respective the frequency Increase in Electrical conductivity found due to the addition of ZnO Particle, Magnetic properties were studied to know the behavior of samples like para magnetic, Ferromagnetic or diamagnetic nature obtained results are discussed. Mechanical properties were investigated to study the stress V/S strain and the results are discussed below

How does thickness affect magnetic coupling in Ti-based MXenes.

The magnetic nature of Ti2C, Ti3C2, and Ti4C3 MXenes is determined from periodic calculations within density functional theory and using the generalized gradient approximation based PBE functional, the PBE0 and HSE06 hybrids, and the on-site Hubbard corrected PBE+U one, in all cases using a very tight numerical setup. The results show that all functionals consistently predict a magnetic ground state for all MXenes, with spin densities mainly located at the Ti surface atoms. The analysis of solutions corresponding to different spin orderings consistently show that all functionals predict an antiferromagnetic conducting ground state with the two ferromagnetic outer (surface) Ti layers being antiferromagnetically coupled. A physically meaningful spin model is proposed, consistent with the analysis of the chemical bond, with closed shell, diamagnetic, Ti2+ like ions in inner layers and surface paramagnetic Ti+ like centers with one unpaired electron per magnetic center. From a Heisenberg spin model, the relevant isotropic magnetic coupling constants are extracted from an appropriate mapping of total energy differences per formula unit to the expected energy values of the spin Hamiltonian. While the numerical values of the magnetic coupling constants largely depend on the used functional, the nearest neighbor intralayer coupling is found to be always ferromagnetic, and constitutes the dominant interaction, although two other non-negligible interlayer antiferromagnetic terms are involved, implying that the spin description cannot be reduced to NN interaction only. The influence of the MXene thickness is noticeable for the dominant ferromagnetic interaction, increasing its value with the MXene width. However, the interlayer interactions are essentially due to the covalency effects observed in all metallic solutions which, as expected, decay with distance. Within the PBE+U approach, a U value of 5 eV is found to closely simulate the results from hybrid functionals for Ti2C and less accurately for Ti3C2 and Ti4C3.