Diamagnetic Susceptibility Research Articles

Structural, optical, XPS, and magnetic properties of Sn–O nanoparticles

Sn–O 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. 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 results indicate that the nanoparticles exhibit 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, 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 XPS. Their density increase accompanies 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.

Tridimensional electric field effect on diamagnetic susceptibility and polarisability of a donor impurity in a double quantum dot

ABSTRACT Theoretical calculations were used to evaluate the response of a tridimensional (spatial) external electric field on the binding energy , polarisability of a hydrogenic donor impurity and diamagnetic susceptibility versus the dot width and the tridimensional electric field intensity , and the impurity location in a double symmetrical quantum dot. The numerical computations were accomplished by utilising the effective mass approximation and the variation method. Our calculations showed that the polarisability diminishes as the applied tridimensional electric field F rises, especially when the dot width is large. Nevertheless, this polarisability is independent of the tridimensional field strength F when the confinement is strong. It has been observed that the degeneracy of the binding energy is broken under the effect of a tridimensional field F. Furthermore, in the absence of a tridimensional field, the diamagnetic susceptibility is symmetric in relation to the centre of the barrier material, having two peaks. However, this symmetry is broken when a spatial electric field is applied.

ANi5Bi5.6+δ (A = K, Rb, and Cs): Quasi-One-Dimensional Metals Featuring [Ni5Bi5.6+δ]- Double-Walled Column with Strong Diamagnetism.

A new series of compounds, ANi5Bi5.6+δ (where A = K, Rb, and Cs) are discovered with a quasi-one-dimensional (Q1D) [Ni5Bi5.6+δ]- double-walled column and a coaxial inner one-dimensional Bi atomic chain. The columns are linked to each other by intercolumn Bi-Bi bonds and separated by an A+ cation. Typical metallic behaviors with strong correlation of itinerant electrons and the Sommerfeld coefficient enhanced with the increasing cationic radius were experimentally observed and supported by first-principles calculations. Compared to AMn6Bi5 (where A = K, Rb, and Cs), the enhanced intercolumn distances and the substitution of Ni for Mn give rise to strong diamagnetic susceptibilities in ANi5Bi5.6+δ. First-principles calculations reveal possible uncharged Ni atoms with even number of electrons in ANi5Bi5.6+δ, which may explain the emergence of diamagnetism. ANi5Bi5.6+δ, as Q1D diamagnetic metals with strong electron correlation, provide a unique platform to understand exotic magnetism and explore novel quantum effects.

Magnetic and Electronic Properties of Edge-Modified Triangular WS2 and MoS2 Quantum Dots

The magnetic and electronic properties of zigzag-triangular WS2 and MoS2 quantum dots are investigated using density functional theory calculations. The pristine WS2 and MoS2 nanodots hold permanent spin on their edges which originates from the unpaired electrons of the transition metals at the edges. The ferromagnetic spin ordering in zigzag-triangular WS2 and MoS2 can be transformed to antiferromagnetic ordering with S = 0 and to nonmagnetic, respectively, by edge passivation with 2H. The calculations of the Curie Temperature indicate that these magnetic states are stable and withstand room temperature. The paramagnetic susceptibility of these structures significantly decreases by edge sulfuration. Moreover, it can be converted to diamagnetic susceptibility by edge passivation with 2H as found in WS2 nanodots. These structures are semiconductors with energy gaps of ~3.3 eV that decrease unexpectedly by edge passivation due to the existence of lone pairs from S atoms that give a high contribution to the low-energy molecular orbitals. With these preferable magnetic properties and controlled electronic ones, WS2 and MoS2 quantum dots are potential candidates for spintronic applications.

Highly effective electromagnetic interference shielding composites with solvent-dispersed uniformly aligned graphene nanosheets enabled by strong intrinsic diamagnetism under magnetic field

Graphene nanosheets (GNS) have been regarded as one of the best fillers in polymers for electromagnetic interference (EMI) shielding composites, but it remains a challenge to prepare well-dispersed and highly aligned GNS for optimal EMI shielding despite many recently developed methods. Here we demonstrate a new technology that not only enables uniform alignment of GNS in polymer composites in any direction but also allows us to systematically tune the composites for optimal EMI performance. The technique makes use of graphene's strong intrinsic and anisotropic diamagnetic susceptibility. Unlike paramagnetism and ferromagnetism, diamagnetism allows us to fully control the orientation of GNS by a rotating magnetic field without causing any aggregation or introducing unwanted magnetic particles due to the repulsive force between GNS. This process for GNS composites further enables us to systematically modify GNS concentration and polymer matrix besides GNS orientations. A record-high shielding effectiveness (SE) of 95 dB is achieved with industrially mass-produced multilayer GNS aligned parallel to the surface of a mixed polyvinylidene fluoride-epoxy composite, and a 50% higher SE is further achieved with few-layer GNS. This technique is scalable, thus opening the practical applications of graphene in EMI shielding.

A review of the applications of magnetic susceptibility measurements for improved reservoir characterization

In the past, the application of magnetic susceptibility of diamagnetic and paramagnetic minerals to the study of rock magnetism was believed to be limited, due to both of their susceptibility signals being small compared to those of minerals in other magnetic. However, recent works have proved the usefulness of diamagnetic and paramagnetic susceptibility for reservoir studies. This paper summarizes results from previous studies showing the application of magnetic susceptibility measurements for characterizing different reservoir properties. Studies on the magnetic susceptibility of crude oils from different oil field regions around the world have shown good correlations of the susceptibility values with crude oil densities as well as other physical and chemical properties. In other studies, the measurements of magnetic susceptibility at the low and high fields have also been applied on rock core samples collected from different types of oil and gas reservoirs such as clastic shoreface, carbonate, shale and oil sand reservoirs. The magnetic susceptibility measurements for core samples without damaging the core by using the probe magnetic technique is probably used as a rapid, reasonable screening method for the initial estimation of core samples. The susceptibility of rock samples does not only show good correspondence with other reservoir characterizing methods, such as downhole gamma ray, spontaneous potential logs and core permeability, but it also shows some advantages over the traditional ones. The results suggested that the measurements of magnetic susceptibility could be used as an independent and improved method for distinguishing crude oil from different types of reservoirs, identifying main lithologies and predicting the permeable zone of a reservoir as well as estimating clay mineral contents.

Combined experimental and computational 1H NMR study of water adsorption onto graphenic materials

The effects caused by the interaction with graphene-like layers on the 1H NMR spectra of water molecules adsorbed onto porous carbon materials were investigated by a combination of shielding calculations using density functional theory (DFT) and 1H NMR experiments. Experimental 1H NMR spectra were recorded for different water-containing carbon materials (activated carbons and milled graphite samples); the 1H NMR signals due to adsorbed water in these materials showed a strong shielding effect caused by the electron currents present in the graphene-like layers. This effect was enhanced for activated carbons prepared at high heat treatment temperatures and for milled graphite samples with short milling times, evidencing that the structural organization of the graphene-like layers was the key feature defining the magnitude of the shielding on the 1H nuclei in the water molecules adsorbed by the analyzed materials. The DFT calculations of the shielding sensed by these 1H nuclei showed an increased interaction with the graphitic layers as the distance between these layers (representing the pore size) was reduced. A continuous decrease of the 1H NMR chemical shift was then predicted for pores of smaller sizes, in good agreement with the experimental findings. These calculations also showed a large dispersion of chemical shifts for the several 1H nuclei in the water clusters, attributed to intermolecular interactions and to shielding variations within the pores. This dispersion, combined with the effects due to the locally anisotropic diamagnetic susceptibility of graphite-like crystallites, are the main contributions to the broadening of the 1H NMR signals associated with water adsorbed onto porous carbon materials.

Theoretical study of the non-parabolicity and size effects on the diamagnetic susceptibility of donor impurity in Si, HgS and GaAs cylindrical quantum dot and quantum disk: applied magnetic field influence is considered

ABSTRACT Through this work, we have investigated the influence of the conduction band non-parabolicity (NP) and magnetic field on the diamagnetic susceptibility for a confined shallow donor impurity in a homogeneous cylindrical quantum dot (CQD) and quantum disk (QDisk); the size effect has been considered. Our calculations have been performed using the variational method which consists of the choice of a trial wave function. The Schrodinger equation has been solved within the effective-mass approximation considering the infinite height potential barrier. The numerical calculations are performed taking into account different semiconductor materials (i.e. Si, HgS and GaAs). Our results reveal that both the size and conduction band NP have a significant impact on the behaviour of the diamagnetic susceptibility for both studied systems (i.e. CQD and QDisk). It has been also noticed that, for both CQD and QDisk, the NP increases the diamagnetic susceptibility (). Furthermore, this effect is remarkable for low band gap semiconductors, especially in large QD (weak radial confinement). However, it is much more important in HgS due to its narrow band gap compared to Si and GaAs materials.

Spin-orbit interaction effects on a [formula omitted] complex in a GaAs quantum dot in a magnetic field

The spin-orbit interaction effects on the energetics of a negative donor centre localized in a 3D Gaussian GaAs quantum dot placed in a magnetic field are studied variationally by using a unitary transformation and a Jastrow function to incorporate the role of Coulomb interaction. The Dresselhaus interaction is shown to increase the binding of the negative donor. The diamagnetic susceptibility and the dipole moment of the system are also calculated.

Study of the Diamagnetic Properties of Liquid Polydimethylsiloxane (PDMS) with the Moses Effect

The relationship between the magnetic susceptibility and degree of polymerization of liquid polydimethylsiloxane (PDMS) was studied experimentally. The magnetic susceptibility of the liquid PDMS was established with the Moses effect, i.e., study of the shape of the near-surface well (the well created near the surface-vapor interface) created in the liquid by a permanent magnetic field. The study of the shape of the near-surface well was carried out under experimental registration of the laser beam reflected from the PDMS/air interface. The broad range of available molecular weights of PDMS made it suitable for the study. The diamagnetic susceptibility, of PDMS was measured for a broad range of molecular weights. The plot of magnetic susceptibility, χ, against the number of repeating units in the chain, n, was linear. The result was compared with the magnetic susceptibility predicted by the Pascal law. The volume magnetic susceptibility of the liquid PDMS was established as = (−7.77 ± 0.06) · 10−6. The magnetic susceptibility of the PDMS monomer was established as χexp (n = 1) = (60.3 ± 0.32) · 10−11, which is in a satisfactory agreement with the Pascal empirical rule.

Effects of applied magnetic field and pressure on the diamagnetic susceptibility and binding energy of donor impurity in GaAs quantum dot considering the non-parabolicity model’s influence

ABSTRACT In this article, we investigate the influence of the hydrostatic pressure, magnetic field, and conduction band non-parabolicity on both the diamagnetic susceptibility and the binding energy of shallow donor impurity in a quantum disk made out of GaAs. The Hamiltonian of the investigated problem has been solved within the framework of the effective-mass approximation. The energy minimisation has been performed using a variational approach. Our results reveal that both the diamagnetic susceptibility and binding energy have been reduced with increasing the disk size. Moreover, the diamagnetic susceptibility increases as the impurity moves from the extremity to the centre of the disk. However, both the diamagnetic susceptibility and binding energy have been improved under applied magnetic field, hydrostatic pressure, and by considering the conduction band non-parabolicity model as well. We hope that the reported results will be a modest contribution to further theoretical research in the field of nanostructures.

Red blood cell magnetophoresis as a function of oxygen partial pressure

Red blood cell (RBC) magnetophoresis is a function of the concentration of dissolved oxygen (O2) in normal RBCs measured by cell tracking velocimetry (CTV). The hemoglobin (Hb) magnetic susceptibility changes from diamagnetic (when fully oxygenated, oxyHb) to paramagnetic (when fully deoxygenated, deoxyHb) resulting in a small shift in the normal RBC diamagnetic susceptibility from lower to higher than that of water (-9.05 × 10-6). To date, the RBC magnetophoretic motion analyses have been limited to only two quaternary states of the Hb-O2 complexes, fully oxygenated RBCs (i.e. 100 % O2 saturation of Hb inside RBCs) and fully deoxygenated RBCs (0 % O2 saturation of Hb inside RBCs). In this work, the RBC magnetophoretic velocity is measured at small pO2 intervals for the entire physiological range of 0–160 mmHg. The changes in the RBC magnetophoresis as a function of the O2 partial pressure in solution (pO2) agreed with the theoretical predictions based on the RBC-O2 equilibrium curve (OEC, measured by Hemox Analyzer and Blood Oxygen Binding System, BOBS™) and the Adair O2-Hb cooperative binding theory. The results provide a scientific basis for future designs of a “magnetic filter” based on the precise control of the RBC magnetic moment by carefully controlling the pO2 of the RBC suspension.

Optical, Charge Transport, Thermal, Magnetic, Plasmonic, and Quantum Mechanical Properties of Iridium

Spectrophotometry has been widely used to retrieve the dielectric function of a bulk iridium sample using an extended version of the Drude–Lorentz model. The parameters of the model are optimized using a spectral-projected-gradient-method-assisted acceptance-probability-controlled simulated annealing approach. Furthermore, optimized values of Drude parameters corresponding to the optical response of electrons and holes (scattering frequency of electrons, the ratio between scattering frequencies of holes and electrons, the ratio between effective masses of electrons and holes, the ratio between the number densities of holes and electrons, and electron volume plasma frequency) are used to evaluate charge transport and magnetic properties. These include static and dynamic conductivities, intrinsic mean free paths, the effective mass of charge carriers and their number densities, Fermi velocities and energies, densities of states at Fermi energies, mobilities, specific heats, Hall’s coefficient, thermal conductivities, charge carrier coupling constant, paramagnetic and diamagnetic susceptibilities, and the number of Bohr magnetons. In addition, optimized resonance energy values of the Lorentz contribution to the dielectric function were compared with the background information provided by density-functional-theory calculations for iridium. A decomposition of the energy loss function was used as the starting point to calculate the effective numbers of bound electrons involved in interband transitions, as well as the densities of states at the final energies of the sets of transitions considered. The Drude–Lorentz model involves charge carrier parameters for both electrons and holes, as well as the resonance energies correlating with the energies associated with quantum transitions. To a large extent, several physical quantities calculated from optimized parameters exhibit values close to those obtained from measurements or by applying other models, including quantum mechanics formulations.

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

Through the present work, we investigated the dielectric screening, temperature and applied magnetic field on donor-impurity diamagnetic susceptibility and binding energy in quantum disk (QDisk) made out of GaAs. Moreover, the influence of the position, hydrostatic pressure, temperature, and magnetic field on the dielectric screening function and the diamagnetic coefficient are also reported. The calculations are performed within the effective-mass theory using variational approach considering an infinite potential barrier. Our results reveal that the variation of QDisk's dimension, temperature, magnetic field and pressure have a considerable impact on diamagnetic susceptibility and binding energy, diamagnetic coefficient (DC) and dielectric screening. It is found that the magnetic field increase the diamagnetic susceptibility and binding energy while the temperature and dielectric screening reduce the diamagnetic susceptibility and improve the binding energy. We hope that the present work exhibits a modest contribution for further theoretical research on GaAs-based nanostructures.

Investigating Some Diatomic Molecules Bounded by the Two-Dimensional Isotropic Oscillator plus Inverse Quadratic Potential in an External Magnetic Field

We investigate the nonrelativistic magnetic effect on the energy spectra, expectation values of some quantum mechanical observables, and diamagnetic susceptibility for some diatomic molecules bounded by the isotropic oscillator plus inverse quadratic potential. The energy eigenvalues and normalized wave functions are obtained via the parametric Nikiforov-Uvarov method. The expectation values square of the position r 2 , square of the momentum p 2 , kinetic energy T , and potential energy V are obtained by applying the Hellmann-Feynman theorem, and an expression for the diamagnetic susceptibility X is also derived. Using the spectroscopic data, the low rotational and low vibrational energy spectra, expectation values, and diamagnetic susceptibility X for a set of diatomic molecules (I2, H2, CO, and HCl) for arbitrary values, Larmor frequencies are calculated. The computed energy spectra, expectation values, and diamagnetic susceptibility X were found to be more influenced by the external magnetic field strength and inverse quadratic potential strength g than the vibrational frequencies and the masses of the selected molecules.

Probing the quantum noise of the spinon Fermi surface with NV centers

We study the transverse electrical conductivity and the corresponding magnetic noise of a two-dimensional U(1) spin liquid state with a spinon Fermi surface. We show that in the quasi-static regime these responses have the same wave-vector dependence as that of a metal but are reduced by a dimensionless pre-factor controlled by the ratio of orbital diamagnetic susceptibilities of the spinons and chargons, correcting previous work. We estimate that this quasi-static regime is comfortably accessed by the typical NV center splittings of a few GHz and estimate that the expected T1 times for an NV center placed above candidate materials, such as the organic dmit and ET salts, monolayer 1T-TaS2/Se2, would range from several tens to a few hundred milliseconds.

Electron spin coherence on a solid neon surface

A single electron floating on the surface of a condensed noble-gas liquid or solid can act as a spin qubit with ultralong coherence time, thanks to the extraordinary purity of such systems. Previous studies suggest that the electron spin coherence time on a superfluid helium (He) surface can exceed 100 s. In this paper, we present theoretical studies of the electron spin coherence on a solid neon (Ne) surface, motivated by our recent experimental realization of single-electron charge qubit on solid Ne. The major spin decoherence mechanisms investigated include the fluctuating Ne diamagnetic susceptibility due to thermal phonons, the fluctuating thermal current in normal metal electrodes, and the quasi-statically fluctuating nuclear spins of the 21Ne ensemble. We find that at a typical experimental temperature about 10 mK in a fully superconducting device, the electron spin decoherence is dominated by the third mechanism via electron–nuclear spin–spin interaction. For natural Ne with 2700 ppm abundance of 21Ne, the estimated inhomogeneous dephasing time is around 0.16 ms, already better than most semiconductor quantum-dot spin qubits. For commercially available, isotopically purified Ne with 1 ppm of 21Ne, can be 0.43 s. Under the application of Hahn echoes, the coherence time T 2 can be improved to 30 ms for natural Ne and 81 s for purified Ne. Therefore, the single-electron spin qubits on solid Ne can serve as promising new spin qubits.

Coexistence of crystalline rhombohedral stacking and hexagonal moiré superlattices in exfoliated highly oriented pyrolytic graphite

The recent observation of unusual persistent currents at the stacking faults of highly-oriented-pyrolytic-graphite (HOPG) has attracted significant attention.In this work, we investigate the structural properties of these systems and especially the possible magnetic effects arising from coexistence of both rhombohedral-stacking and hexagonal moiré -superlattices, within exfoliated samples. Raman spectroscopy and X-ray diffraction (XRD) allowed for the identification of hexagonal and rhombohedral graphitic structural-components coexisting within manually-exfoliated thick HOPG-samples (thickness of ~ 300–400 µm). Comparative characterization of thin (thickness of ~ 0.1–10 µm) samples revealed a significant weakening of the rhombohedral-component, highlighting a rapid ABC to AB relaxation. This interpretation was further confirmed by TEM analyses performed on thin-samples (e-beam perpendicular to the layers). Noticeably, the unusual presence of large-area hexagonal-moiré -superlattices in coexistence with rhombohedral domains could be identified in one of the analysed lamellae. The unusual grain-boundary between the two phases was analysed in relation to the possible variation of the θ-twist parameter. Disappearance of the superlattices was found in those disclination-rich regions created by the exfoliation process. Magnetic characterization of both thick and thin samples, allowed for the identification of an unusual overlay between zero field cooled (ZFC) and field cooled (FC) magnetic signals, with a T-dependent enhancement of the diamagnetic susceptibility from T~ 300 K to T~2 K, possibly resulting from a disclination-free structural configuration. A spin-glass-like behaviour was instead found in those samples exhibiting a broader and disorder-rich non-monotonic X-ray rocking-curve distribution.

Anomalous broadening of Landau levels at the saddle point energy of two dimensional square lattice

We study the magnetic characteristics of the two dimensional (2D) square lattice with one valence electron per lattice site in weak rational magnetic fields accessible experimentally, by solving numerically the exact system of discrete equations, which fully describes the broadening of Landau levels. The 2D square lattice is used as a prototype electron system in which the Fermi level lies at the energy of the saddle point (Van Hove peak) of the Brillouin zone and the corresponding density of states N(EF) is formally infinite (N(EF)→+∞). According to the electron band treatment this could lead to a formally divergent paramagnetic susceptibility and an infinite electron contribution to the specific heat at zero temperature, but our accurate analysis shows that both values remain finite. The energy spectrum of the Landau level at the saddle point has turned out to be principally continuous, so that even in a very small magnetic field this Landau level is always broadened in a miniband, in contrast to other energies, where the spectrum of Landau levels is discrete. Taking into account the electron spin polarization and the numerical solution, we reproduce the temperature dependence of the induced magnetic moment proportional to the magnetic susceptibility, and the electron contribution to the specific heat. Both plots demonstrate unusual dependencies reflecting the “metal”-like or “insulator”-like structure of the Landau minibands in the neighborhood of the Fermi energy. At low temperatures all values display oscillatory behavior. We also prove rigorously that the fully occupied electron band has no contribution to the diamagnetic susceptibility and specific heat.

Inertial Term Accounting in Navier-Stokes Equation of Magnetohydrodynamic Domains Model for a Nematic with Negative Anisotropy of Diamagnetic Susceptibility

Inertial Term Accounting in Navier-Stokes Equation of Magnetohydrodynamic Domains Model for a Nematic with Negative Anisotropy of Diamagnetic Susceptibility