Diamagnetic Susceptibility Research Articles

Account for the Inertial Term in the Navier–Stokes Equation in the Model of Magnetohydrodynamic Domains for Nematics with Negative Anisotropy of Diamagnetic Susceptibility

Account for the Inertial Term in the Navier–Stokes Equation in the Model of Magnetohydrodynamic Domains for Nematics with Negative Anisotropy of Diamagnetic Susceptibility

Magnetic properties of oxides and silicon single crystals

The magnetic properties of single crystals Si, SrTiO3, LaAlO3, MgO, and (La,Sr)(Al,Ta)O3 were investigated systematically. Three origins of the magnetizations of these crystals, namely, an intrinsic diamagnetic, a paramagnetic, and a ferromagnetic contribution, have been found to influence the magnetic signals measured on the crystals, in some important application scenarios such crystals being served as substrates with the magnetic thin film epitaxially grown on. Quantitative analyses methodologies were developed and thorough investigations were performed on the crystals with the intrinsic materials parameters thus revealed, especially that the intrinsic diamagnetic susceptibility differential dχ dia/dT were identified quantitatively for the first time in SrTiO3, LaAlO3, MgO, and (La,Sr)(Al,Ta)O3. The paramagnetic contribution is found to be the key in terms of the magnetic properties of the crystals, which in turn is in fact a consequence of the 3d impurities doping inside the crystal. All the intrinsic materials parameters are given in this paper as datasets, the datasets are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00028.

Blip up-down acquisition for spin- and gradient-echo imaging (BUDA-SAGE) with self-supervised denoising enables efficient T2 , T2 *, para- and dia-magnetic susceptibility mapping.

To rapidly obtain high resolution T2 , T2 *, and quantitative susceptibility mapping (QSM) source separation maps with whole-brain coverage and high geometric fidelity. We propose Blip Up-Down Acquisition for Spin And Gradient Echo imaging (BUDA-SAGE), an efficient EPI sequence for quantitative mapping. The acquisition includes multiple T2 *-, T2 '-, and T2 -weighted contrasts. We alternate the phase-encoding polarities across the interleaved shots in this multi-shot navigator-free acquisition. A field map estimated from interim reconstructions was incorporated into the joint multi-shot EPI reconstruction with a structured low rank constraint to eliminate distortion. A self-supervised neural network (NN), MR-Self2Self (MR-S2S), was used to perform denoising to boost SNR. Using Slider encoding allowed us to reach 1 mm isotropic resolution by performing super-resolution reconstruction on volumes acquired with 2 mm slice thickness. Quantitative T2 (=1/R2 ) and T2 * (=1/R2 *) maps were obtained using Bloch dictionary matching on the reconstructed echoes. QSM was estimated using nonlinear dipole inversion on the gradient echoes. Starting from the estimated R2 /R2 * maps, R2 ' information was derived and used in source separation QSM reconstruction, which provided additional para- and dia-magnetic susceptibility maps. In vivo results demonstrate the ability of BUDA-SAGE to provide whole-brain, distortion-free, high-resolution, multi-contrast images and quantitative T2 /T2 * maps, as well as yielding para- and dia-magnetic susceptibility maps. Estimated quantitative maps showed comparable values to conventional mapping methods in phantom and in vivo measurements. BUDA-SAGE acquisition with self-supervised denoising and Slider encoding enables rapid, distortion-free, whole-brain T2 /T2 * mapping at 1 mm isotropic resolution under 90 s.

Impurity effects on binding energy, diamagnetic susceptibility and photoionization cross-section of chalcopyrite AgInSe2 nanotadpole

Recently the interest in chalcopyrite semiconductor nanostructures has increased because of their non-toxicity and their wide direct bandgap. Likewise, structures with non-trivial geometry are particularly interesting because of their electronic, optical, and magnetic properties. In the current article, the finite element method was used in conjunction with the effective mass approximation to theoretically investigate the properties of a chalcopyrite AgInSe2 nanotadpole in the presence of an hydrogen like shallow off-center impurity. The morphology of the nanotadpole gives it excellent hydrodynamic properties and is ideal for a wide range of applications. The probability densities for various impurity positions and energy levels were obtained. The results suggested a strong dependence of the behavior of the electron on the impurity positions and the orientation of the wave function. The investigation of the nanotadpole’s energy spectra and their comparison with the cylindrical and spherical quantum dots suggest that the spectrum has degenerate states similar to the spherical case, however at some ranges, the levels behave similarly to the cylindrical case. The binding energy’s dependence on the nanotadpole’s size and the impurity position was obtained. The dependence of the diamagnetic susceptibility on the impurity position was calculated. An extensive investigation of the photoionization cross-section was carried out for the ground and the first two excited states as the initial states and the first twenty excited states as the final states.

Can van der Waals constants be used in the chemical reactivity analysis? A new approach as a support to minimum magnetizability principle

AbstractOne of the most important purposes of theoretical chemists is to derive new, useful, and reliable equations to compute the well‐known parameters like hardness, polarizability, magnetizability, and electrophilicity providing enough hints for the reactivity analysis of the chemical systems. In the derivation of such equations, our research team widely considers the popular electronic structure rules like electronegativity equalization, maximum hardness, minimum polarizability, minimum magnetizability, and minimum electrophilicity principles. Recently, in the light of maximum entropy and minimum magnetizability principles, Kaya and Chattaraj (2021) presented a simple way to calculate their standard absolute entropies (S0298) based on molar diamagnetic susceptibilities (χm) of inorganic ionic systems. In the present paper, a new and useful molar diamagnetic susceptibility calculation method including the use of van der Waals constants (a and b) is introduced. Here, we named this method as Kaya–Şimşek approach. Through the relations between molar diamagnetic susceptibility and van der Waals constants, we can easily predict the magnetic susceptibility of molecules that their magnetic susceptibilities are unknown. The results of the equations derived are quite close to experimentally reported data. The analyses made proved that van der Waals constants can be considered as chemical reactivity descriptors. We propose that in stable states, van der Waals constants are minimized. The validity of minimum magnetizability principle is supported with solid evidences.

New Insights into the Magnetic Properties of CoFe2O4@SiO2@Au Magnetoplasmonic Nanoparticles

We report the successful synthesis and a complete magnetic characterization of CoFe2O4@SiO2@Au magnetoplasmonic nanoparticles. The CoFe2O4 magnetic nanoparticles were prepared using the hydrothermal method. A subsequent SiO2 shell followed by a plasmonic Au shell were deposited on the magnetic core creating magnetoplasmonic nanoparticles with a core–shell architecture. A spin-glass-type magnetism was shown at the surface of the CoFe2O4 nanograins. Depending on the external magnetic field, two types of spin-glass were identified and analyzed in correlation with the exchange field acting on octahedral and tetrahedral iron sites. The magnetization per formula unit of the CoFe2O4 core is not changed in the case of CoFe2O4@SiO2@Au nanocomposites. The gold nanoparticles creating the plasmonic shell show a giant diamagnetic susceptibility, dependent on their crystallite sizes.

Binding energy, polarizability, and diamagnetic response of shallow donor impurity in zinc blende GaN quantum dots

In this theoretical investigation, the binding energy, the binding energy Stark-shift, the dipole moment, the polarizability, and the diamagnetic susceptibility related with a confined shallow donor impurity in zinc blende GaN conical-shaped quantum dots are calculated under the effect of an electric field applied along the z-direction. Calculations have been made by using a variational approach within the infinite confining potential model and considering the parabolic conduction band and the effective mass approximations. The results suggest important dependencies of the calculated physical properties on the variation of the dot dimensions, axial impurity position, and the intensity of the applied electric field. It is observed that: i) the binding energy Stark shift increases up to a maximum value and then decreases with increasing the strength of the electric field, and it is strongly influenced by the impurity position and geometrical parameters, ii) for a fixed electric field value, the binding energy Stark shift is always an increasing function of the dot height, and iii) for fixed electric field values, the binding energy Stark shift shows a mixed behavior concerning the dot radius, i.e., for low field strength, the binding energy is always a growing function of the radius, and for large field strengths, such physical quantity grows with the radius up to a maximum and then decreases. Furthermore, the electric field (the strong quantum confinement) enhances slightly (diminishes) the diamagnetic susceptibility of impurity.

Structural, optical, magnetic, and XPS properties of SnOx nanoparticles

SnOx nanoparticles ranging in average particle sizes from 13 to 420 nm have been prepared by levitation-jet aerosol synthesis through condensation of tin vapor in a mixed flow of inert gases and air/oxygen. X-ray diffraction (XRD) established the presence of mixed-phase of Sn, SnO, and SnO2 components in the nanoparticles. During optical measurements, the redshift of bandgaps was discovered in nanoparticles with SnO2 content <80% and blue shift in nanoparticles with SnO2 content >80%. The samples were examined for their magnetic properties using a vibrating sample magnetometer (VSM) and indicate room-temperature ferromagnetism. The maximum net saturation magnetization observed in the studied nanoparticles is ≈ 7 memu/g near a Sn/O molar ratio of ≈0.58. Moreover, an excess magnetic contribution (from oxygen vacancies), either as paramagnetic or as diamagnetic susceptibility, has been observed. Raman studies found the presence of small amounts of Sn3O4 or Sn2O3 phases in the nanoparticles. The presence of oxygen vacancies in the nanoparticles was established by X-ray photoelectron spectroscopy (XPS). Their density increase is probably accompanied by the saturation magnetization enhancement. We propose that the presence of definite localized states, like interacting and non-interacting vacancies on the Sn/SnO and SnO/SnO2 interfaces, is responsible for the observed magnetic phenomena.

Diamagnetic susceptibility from a nonadiabatic path-integral simulation of few-electron systems

Diamagnetism is the response of dynamical compositions of charged particles, electrons, and nuclei, to an incident magnetic field. In this paper, we study how the finite temperature and finite nuclear masses affect the diamagnetic susceptibilities of selected small atoms and molecules, as limiting cases of dilute gas. We use nonrelativistic path-integral Monte Carlo simulation (PIMC), where both electrons and nuclei are treated on equal footing at finite temperatures in sampling exact Coulomb pair density matrices. The PIMC estimator of diamagnetic susceptibility has been briefly introduced in Ceperley [D. M. Ceperley, Rev. Mod. Phys. 67, 279 (1995)], but here we present a comprehensive derivation, discussion of practical effects, and proof-of-concept results for selected few-body Coulomb systems. Our results are in perfect agreement with high-accuracy literature references, where available, but also demonstrate additional thermal effects of the diamagnetic response of low-mass systems.

Tuning of optoelectronic and transport properties of zinc-blend magnesium chalcogenides through doping of Hg atom(s): The mBJ-GGA+U based first-principle calculations

The present first-principle calculations have established the possibility of tuning of structural, optoelectronic and transport properties of direct-band-gap and optically active zinc-blend magnesium chalcogenides through doping of Hg atom(s) at different compositions. The process results a set of thermodynamically stable, direct-band-gap and optically active HgxMg1-xS, HgxMg1-xSe and HgxMg1-xTe semiconductor ternary alloys. Non-linear enhancement in lattice constant (a0), but reduction in fundamental band-gap (Eg) takes place in each system with increasing Hg-composition (x). Electrons and light holes possess much smaller effective-mass compared to heavy holes in each specimen. Calculations show positive Seebeck coefficient and hence p-type conduction property of each ternary alloys. Calculated electronic figure-of-merit shows that ternary alloys are suitable for efficient thermoelectric applications beyond 900 K temperature. Electronic excitations from valence chalcogen-p level to Mg-4s, 3p and Hg-7s levels of conduction band region of band-structure near Fermi-level put significant contributions in diverse optical phenomenon in the UV region, which lead to their compatibility in fabricating diverse UV optoelectronic devices. Oscillator strength, optical energy-gap, skin-depth, optical electronegativity difference, electronic polarizability and diamagnetic susceptibility of each of the considered specimens are also calculated in the present study.

The role of 4f14 Lu3+ and 3d0 Sc3+ in faraday rotating glass/ceramic: Structural stability, magnetic and magneto optical properties

Magneto-optical materials exhibiting low/no temperature-dependent Faraday rotation, high magnetization and good thermal/mechanical stability are required in various magneto-optical sensing and photonic applications. For the first time, we employed the rare earth Lu3+ and Sc3+ ions to strengthen the structure and enhance magnetic& magneto-optical properties of heavy metal oxide diamagnetic glasses. Experimental results revealed that the doping of Lu2O3 and Sc2O3 not only significantly increased the UV-VIS transmittance, improved the thermal stability, Vicker's hardness and tensile strength, but also remarkably increased the magnetic susceptibility and Verdet constant. The reasons were analyzed through the XRD, FT-IR, Raman spectra, oxygen chemical bonds, EPR of Lu2O3 and Sc2O3 crystal fields and affinity to oxygen. Promising Faraday rotating glass with Verdet constant of 76.32 rad/Tm at 633 nm, thermal stability KH = 0.817, very low thermal expansion coefficient (14.04 × 10−6 K−1) and high diamagnetic susceptibility of 9.25 × 10−6 emu/g has obtained which has potential merits for photonics and MO devices applications.

Temperature dependences of electrical conductivity and magnetic susceptibility of crystals of solid solution Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=--Bi-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-

Solid solutions Bi2Te3-Sb2Te3 continue to be the subject of numerous and versatile experimental studies due to their practical importance for thermoelectric materials science. In this regard, the problem of studying the regularities of changes in the state of the electronic system of these semiconductors from composition and temperature remains urgent. This paper presents the results of studying the temperature dependences of the magnetic susceptibility of Bi2Te3-Sb2Te3 crystals containing 10, 25, 40, 50, 60 mol.% Sb2Te3. The correlation of the behavior of the temperature dependences of the magnetic susceptibility and electrical conductivity is analyzed. Keywords: magnetic susceptibility, diamagnetic susceptibility, temperature dependence of electrical conductivity.

The Effects of the Dielectric Screening, Temperature, Magnetic Field, and the Structure Dimension on the Diamagnetic Susceptibility and the Binding Energy of a Donor-Impurity in Quantum Disk

The Effects of the Dielectric Screening, Temperature, Magnetic Field, and the Structure Dimension on the Diamagnetic Susceptibility and the Binding Energy of a Donor-Impurity in Quantum Disk

Theoretical approach to estimate Molecular Polarizability and Diamagnetic Susceptibility of 6O.CB and 10O.CB Mesogens

Theoretical approach to estimate Molecular Polarizability and Diamagnetic Susceptibility of 6O.CB and 10O.CB Mesogens

Physical properties of rhodium retrieved from modeling its dielectric function by a simulated annealing approach

Optical, charge carriers transport, quantum mechanics, magnetic, thermal, and plasmonic properties of the transition metal rhodium are considered. An extended Drude-Lorentz (DL) model is applied to describe the dielectric function (DF) of rhodium in a spectral range going from the mid-infrared (12.4 μm) to the vacuum ultraviolet (32 nm). The Drude term of the DF includes, as optimization parameters, the inverse of the high frequency dielectric constant, the volume plasma frequency and scattering frequency of the electrons, the scattering frequency of holes relative to that of electrons, the ratio between the effective masses of electrons and holes, the number of holes per atom relative to that of electrons, and the renormalized times between grain boundary scattering events for electrons and holes. The Lorentz contribution to the DF includes the number of conduction electrons per atom, the oscillator strengths, the resonance energies, and the Lorentzian widths. Values of the parameters involved in the DF are optimized by an acceptance-probability-controlled simulated annealing method that minimizes spectral differences between the real and imaginary parts of the DF values obtained from the literature and those evaluated from the DL parametric formulation, accounting for the presence of electrons and holes as charge carriers. Once an optimized spectral description of the DF of rhodium is obtained, a large set of charge-transport, magnetic, thermal, plasmonic, and quantum mechanics derived quantities are evaluated: mobilities, relaxation times, Fermi velocities, effective masses, electrical and thermal conductivities, heat capacity coefficients, Hall coefficient, diamagnetic and paramagnetic susceptibilities, effective number of Bohr magnetons, Fermi energies and corresponding densities of states, energy loss functions, effective number of charge carriers participating in conduction, and effective number of electrons involved in inter-band transitions.

Magnetic Torque due to Anisotropic Diamagnetism in Neutral BEDT-TTF Crystals

Magnetic susceptibility and torque measurements have been performed for neutral BEDT-TTF crystals to investigate the diamagnetic properties. The diamagnetic susceptibility is found to be anisotropi...

Hydrostatic pressure and temperature effects on spectrum of an off-center single dopant in a conical quantum dot with spherical edge

In this paper we have studied the spectrum of an off-center donor impurity confined in the GaAs conical quantum dot with spherical edge surrounded by finite and infinite confinement potential. By considering the effective mass approximation and using the finite difference and elements method, we have obtained the eigenenergies and the eigenfunctions of the nanosystem. The hydrostatic pressure and temperature effects as well as the displacement of the donor on the binding energy are investigated. Within the confinement effect, the variation of the dot angle and the radius of the conical quantum dot on the electron-donor properties are evaluated. The numerical findings show that the binding energy is very sensitive to the position of the impurity and the size of the conical quantum dot (radius and dot angle). The position of the donor impurity leads to control the way of the variation of the binding energy versus the conical angle. The study includes the effects of hydrostatic pressure and temperature. It is noted that the binding energy increases with hydrostatic pressure and decreases with temperature. Additionally, the results show that the diamagnetic susceptibility increases with the conical angle and decreases with the dot radius. Therefore, it has an effective influence on the small radius of the quantum cone. In addition, we have examined extensively the possible effect due to change of the geometric angle and different position of impurity on the permanent dipole moment created by the electron and the ionized atom. Our results indicate that the spectrum of the impurity is strongly related to the impurity positions and the dot angle of the nanodot. These different influences allow a good understanding of the spectrum of these nanoparticles, and facilitate the fabrication of new optoelectronic devices.

Orbital dynamics in 2D topological and Chern insulators

Within a relativistic quantum formalism we examine the role of second-order corrections caused by the application of magnetic fields in two-dimensional topological and Chern insulators. This allows to reach analytical expressions for the change of the Berry curvature, orbital magnetic moment, density of states and energy determining their canonical grand potential and transport properties. The present corrections, which become relevant at relatively low fields due to the small gap characterizing these systems, determine the zero-field diamagnetic susceptibility of non-zero Berry curvature systems and unveil additional contributions from the magnetic field.

Diamagnetic anisotropy and rotational viscosity of 6CHBT nematic liquid crystal

Nematic liquid crystal with polar terminal NCS group was studied by using acoustic and electro-optical methods. Experimental results on rotational viscosity have been obtained by two methods. The anisotropy of diamagnetic susceptibility of the studied LC with temperature variation was determined based on the comparison of these methods. The present results may be useful for testing physical models of the orientation dynamics of nematic liquid crystals in alternating electric and magnetic fields.

Quantitative Susceptibility Mapping of the Basal Ganglia and Thalamus at 9.4 Tesla.

The thalamus (Th) and basal ganglia (BG) are central subcortical connectivity hubs of the human brain, whose functional anatomy is still under intense investigation. Nevertheless, both substructures contain a robust and reproducible functional anatomy. The quantitative susceptibility mapping (QSM) at ultra-high field may facilitate an improved characterization of the underlying functional anatomy in vivo. We acquired high-resolution QSM data at 9.4 Tesla in 21 subjects, and analyzed the thalamic and BG by using a prior defined functional parcellation. We found a more substantial contribution of paramagnetic susceptibility sources such as iron in the pallidum in contrast to the caudate, putamen, and Th in descending order. The diamagnetic susceptibility sources such as myelin and calcium revealed significant contributions in the Th parcels compared with the BG. This study presents a detailed nuclei-specific delineation of QSM-provided diamagnetic and paramagnetic susceptibility sources pronounced in the BG and the Th. We also found a reasonable interindividual variability as well as slight hemispheric differences. The results presented here contribute to the microstructural knowledge of the Th and the BG. In specific, the study illustrates QSM values (myelin, calcium, and iron) in functionally similar subregions of the Th and the BG.