Diamagnetic Research Articles

Boosted spintronic properties in triangular Si-based nanoflakes

We investigate the magnetic properties of triangular silicene, silicon carbide, Si2BN, and their heterostructures using first principles calculations. Hydrogenation of surface Si atoms significantly enhances the net spin of silicene to 3n/2, n is the number of edge atoms, with perfect distribution only on the zigzag edges. The attached hydrogen prevents π-bonds formation between surface and edge Si-atoms, which provides all silicene edge atoms with unpaired p-orbital electrons to form half-filled states. Silicon carbide with C-/Si- edge atoms has ferromagnetic/antiferromagnetic ordering because of the formation of planer/edge-buckled structure; buckling at the edges arranges the topologically frustrated edge atoms in opposite directions making a net spin of 0zero. Stacking in heterostructures removes the magnetic ordering by forming interlayer π-bonds between edge atoms while twisting one of the layers may isolate some of edge atoms and retain the ferromagnetic state. All the considered flakes are diamagnetic materials with highest diamagnetism in silicene and its heterostructures. However, attaching iron oxide (Fe2O3) to the interactive Si-surface atoms transforms silicene to paramagnetic material, with positive net magnetic susceptibility. In addition to the improved magnetic properties, the electronic properties are also controllable. Thus, these flakes are promising candidates for performant semiconductor spintronics.

Monitoring magnetic susceptibility and spatial distribution of soil attributes in different land uses: a case study in an arid and semi-arid region, southern Iran

The magnetic susceptibility (MS) technique could be used as an efficient tool for management, monitoring, and analysis of soil properties. This study was conducted to investigate the relationship among the magnetic parameters and soil surface properties as well as their spatial variation in different land uses in Fars Province, southern Iran. Three dominant land uses in the study area including cropland, barren, and pasture were selected, and a total of 72 samples were collected from the soil surface (0–15 cm). Physicochemical properties, total free (Fed) and amorphous (Feo) iron forms, and MS in both high (xhf) and low (xlf) frequencies were determined. The results showed a significant difference (p˂0.05) for xlf average values among different land uses which were decreased in the order of cropland (45.31× 10−8 m3 kg−1), barren (31.68 × 10−8 m3 kg−1), and pasture (17.84 × 10−8 m3 kg−1), respectively. There was a positive significant correlation (p <0.01) between the MS values and Fed and Fed-Feo, while a negative significant correlation was observed among xlf and EC, gypsum, and Feo/Fed. The spherical model suitably described the spatial behavior of magnetic parameters and soil properties. The spatial distribution maps represented an almost parallel pattern in the spatial variations of MS, Fed, Fed-Feo, and evolution index, but an inconsistent pattern for Feo, CaCO3, gypsum, and EC in the study area. This indicates the role of diamagnetic materials in decreasing the soil magnetic properties. Results of this study clearly revealed that the MS technique is of great potential in monitoring the spatial variations of soil properties.

Mean inner potential of graphite measured by electron holography: Probing charge distribution and orbital diamagnetic susceptibility

The mean-inner-potential (MIP) of a crystal is the average electrostatic Coulomb potential within a crystal with respect to vacuum.We conducted off-axis electron holography experiments on highly-oriented-pyrolytic-graphite (HOPG) in a transmission-electron-microscope to measure the MIP from nanometer-scale volumes of Bernal graphite oriented with respect to the electron beam, along the principal-axis or directions in the basal plane. These MIP were related to mean orbital electron radii and diamagnetic susceptibilities in perpendicular planes.These measurements are interesting compared to magneto-transport measurements, which report large anisotropy. Along the principal-axis, the susceptibility is highest amongst diamagnetic materials. However, those measurements vary significantly depending on type, size, and thickness of samples, indicating that the signal is significantly extrinsic due to defect induced interfaces. Indeed, structural examination of HOPG show stacking-faults and planar rotations around the principal-axis, such that measuring intrinsic properties requires probing a volume of ∼102 × 102 × 102 nm3.Experiments on such individual graphite crystals with (0001) basal, or (1–100), (2-1-10) prismatic planes, resulted in MIP of 10.16 ± 0.40V, 11.37 ± 0.35V, 12.66 ± 0.41V, respectively. First-principles calculations confirm these anisotropic measurements with 11.72V, 13.65V, 14.56 V, respectively.These measured MIP enable to determine projected mean-radii of electron orbitals and volume susceptibilities at 0.704 ± 0.015 Å, (−1.99 ± 0.08) × 10−5; 0.744 ± 0.015 Å, (−2.23 ± 0.07) × 10−5; 0.785 ± 0.015 Å, (−2.48 ± 0.08) × 10−5.

Structural, optical, magnetic and Faraday rotation properties of MnSe2: Eu doped diamagnetic materials: The impact of multi-valence states of Mn and Eu

Rare earth ions coupled magnetic, electronic and magneto-optical properties of transition metal dichalcogenides are attractive due to interaction of lattice, spin and electronic degree of freedom. For the first time, Eu doped MnSe2 nano-cubes were synthesized and characterized, and the influences to structural and properties of Faraday rotating glass were studied. The introduction of mixed valence states of Eu disturbed the self-assembly of MnSe2 and enhanced the antiferromagnetism due to the vacancies induced by the charge neutral and radius/electronegativity difference. Mn0.9Eu0.1Se2 presenting smaller grain size and better crystallization was selected as dopant to heavy metal oxide glass matrix. The rich energy levels of significant d-d, f-f electron transitions of Mn and Eu ions in Mn0.9Eu0.1Se2 contributed to the improvement of optical linear and nonlinear properties. The band gaps of glasses were decreased and the absorption edges red-shifted. Meanwhile, the third nonlinearity was improved due to increase of polarizability. The spin interactions and electrons charge interactions between Eu and Mn ions in glass provided complex magnetization changing from diamagnetic, paramagnetic and antiferromagnetic. 3% of Mn0.9Eu0.1Se2 functionalized glass showed excellent optical emission at 560 nm and 620 nm wavelengths, good nonlinear coefficient (5.88 × 10−14 esu), high paramagnetic moment (8.28 × 10−6 emu/mol) and giant Verdet constant value (63.998 rad/T/m at 633 nm).

Development and validation of an analytical methodology for quantification of Al in alumina-based materials by 27Al Solid-state nmr

In this work, a simple protocol for counting the Al spins present in diamagnetic materials used as carriers and catalysts based on 27Al solid-state nuclear magnetic resonance using routine 4 mm rotors was developed and validated. The acquisition parameters were optimized, and validation tests were performed using a standard sample of γ-alumina with a known aluminium concentration. The validation results indicated that solid-state NMR can be used for the quantification of quadrupolar aluminium (mmol Al.g-1 material) in diamagnetic materials by employing non-special tools with satisfactory results, similar to the NMR quantitative analysis of dipolar nuclei in solids.

Effect of Bound Polaron and Electromagnetic Field on Thermodynamic Properties of GaAs Quadratic Quantum Dot

The effect of bound polaron on the thermodynamic properties of GaAs quantum dot (QD) with a quadratic potential in the presence of electromagnetic field is presented. The Schrodinger method as well as the canonical ensemble approach has been used to determine the energy of polaron and the thermodynamic properties such as heat capacity, entropy, and magnetic susceptibility with the help of canonical partition function. We found that the heat capacity increases with a potential confinement angle and also with temperature, and decreases with the increase in the magnetic field. This reduction in the heat capacity shows that our system behaves as a refrigerator. Furthermore, an increasing in magnetic field reduces the disorder in the quantum dot. Indeed, a strong increase in the magnetic field is much better for a good confinement of particles. Moreover, we found that the materials with low coupling constant avoid disorder in the quantum system. The polaron is therefore a good protector of the quantum dot against the external effects. We also found that an increasing temperature increases the speed of electrons and also for very small values of magnetic field, the system stores more energy. It is worthy to mention that our approach is consistent with the characteristic behavior of the diamagnetic materials, well-known as GaAs quantum dots.

Mixed valence effects in TbVO4: Y nanocrystals and diamagnetic materials: Structure, optical linear & nonlinear, magnetic and Faraday rotation properties

Diamagnetic Y3+ ions doped magneto-optical TbVO4 nanocrystals were synthesized and characterized, the influence of mixed valence effect in TbVO4: Y to structure and properties of diamagnetic glasses/ceramic was studied. 80–100 nm spherical TbVO4 nanocrystals were hydrothermally synthesized. The doping of 30% and 40% Y3+ into TbVO4 increased the grain size to 120–150 nm and transformed pure zircon-type to a combination of zircon- scheelite type structure. EDX, Raman and infrared spectra revealed that the Y3+ occupied the site of Tb3+ with chemical formula of Tb0.7Y0.3VO4 and Tb0.6Y0.4VO4 respectively. More than 40% Y3+ could not be incorporated into TbVO4 lattice. Y doped TbVO4 nanocrystals presented two absorption peaks at 266 nm and 301 nm and one broad emission peak centered at 468 nm. A quenching of emission was observed for 40%Y doped TbVO4 due to the non-radiation energy transfer between Tb3+ and Y3+. Three nanocrystals displayed EPR resonance signal at g = 1.98 for V4+ ions due to the ion (oxygen) vacancies and structure deformation. VSM and XPS results indicated that the Y3+ doping changed paramagnetic to diamagnetic due to the increase concentration of diamagnetic Y3+, V5+ and Tb4+ ions. Three nanocrystals doped diamagnetic glass/ceramic presented different transparency, homogeneity and structures because of multivalence states of Tb and V in glasses/ceramic. Pure TbVO4 and TbVO4:30%Y doped glasses exhibited transition 7F0→5D2 of Tb3+ and 2B2 g→2B1 g of V4+ ions which resulted in the reduction of band gap energy and red-shifts of absorption edges. A quenching of 5D4→7F5–2 transition of Tb3+ was observed in Tb0.6Y0.4VO4 doped ceramic. Closed and open-aperture Z-scan showed an enhancement of nonlinearity due to the increase of polarizability. The mixed valence states of Tb and V yielded different magnetization and magneto optical rotation performances in glasses/ceramic. TbVO4:30%Y doped glass exhibited remarkable third nonlinear susceptibility (7.66 × 10−11 esu), magnetization and Verdet constant (0.2248 min/G.cm) at 633 nm.

Diamagnetic interactions in superheated-superconducting microgranules under an external magnetic field

L'estudi de les transicions produides en conjunts de granuls superconductors metastables te nteres tant per a la fisica fonamental com per a aplicacions com ara els detectors de particules. L'estudi teoric d'aquest problema ha estat obstaculitzat per la dificultat del tractament de les interaccions diamagnetiques entre granuls. En aquesta revisio descrivim el comportament d'aquests sistemes, desenvolupem el metode numeric del tractament i presentem uns quants resultats experimentals i numerics.

Paramagnetic and Diamagnetic Susceptibility of Infinite Quantum Well

Paramagnetism and diamagnetism of a material characterized by its magnetic susceptibility. When a material is exposed to an external magnetic field, magnetic susceptibility is defined as the ratio of the induced magnetization and the magnetic field. A paramagnetic material has magnetic susceptibility with positive sign. On the other hand, a diamagnetic material has magnetic susceptibility with negative sign. Atomically, paramagnetic materials consist of atoms that has orbital with unpaired electrons. Theoretical study of paramagnetic susceptibility and diamagnetic susceptibility are well described by Pauli paramagnetism and Landau diamagnetism, respectively. Although paramagnetism and diamagnetism are among the simplest magnetic properties of material that are studied in basic physics, theoretical derivations of Pauli paramagnetic and Landau diamagnetic susceptibility require second quantization formalism of quantum mechanics. We aim to discuss the paramagnetic and diamagnetic susceptibilities for simple three-dimensional quantum well using first quantization formalism.

Special Issue: “Optical Thin Films and Structures: Design and Advanced Applications”

This Special Issue is devoted on design and application of thin films and structures with special emphasis on optical applications. It comprises ten papers, five featured and five regular papers, authored by respective scientists all over the world. Diverse materials are studied and their possible applications are demonstrated and discussed: transparent conductive coatings and structures from ZnO doped with Al and Ga and Ti-doped SnO2, polymer and nanosized zeolite thin films for optical sensing, TiO2 with linear and non-linear optical properties, organic diamagnetic materials, broadband optical coatings, CrWN glass molding coatings and silicon on insulator waveguides.

Simulation of magnetic transitory parameters at electromagnetic forming of metal sheet

Proposed and accomplished finite element simulations in this paper started from the idea that materials which are plastically deformed and those from which electromagnetic deformation devices are built can influence the development of transitory magnetic phenomenon during the working process. Workpieces from paramagnetic, diamagnetic and ferromagnetic materials and devices that contain metallic and non-metallic materials were taken into study. FLUX2D modelling and simulating software was used to achieve numerical values and graphical images for the main process parameters: magnetic induction and magnetic pressure (of deformation). A finite element model, previously validated through experiment, was used to perform the simulations in order to assure a high degree of accuracy for the presented results.

Experiment and simulation of the effects of non-uniform magnetic field on the regression rate of PMMA

Burning rate modulation of solid fuel can improve the performance of solid fuel ramjet over a wider altitude or Mach number envelopes. To better control the burning rate of a solid fuel, the effect of magnetic fields on the regression rate of solid fuel was experimentally and numerically investigated. In this experiment, the regression rates of polymethyl methacrylate (PMMA) rods under different types of magnetic field gradients were measured. Meanwhile, the morphological changes in the flame during combustion were recorded by a complementary metal-oxide semiconductor (CMOS) camera. The experimental results indicated that the regression rate for PMMA varies regularly with various magnetic field gradients, with rates in the range from -32.5% to 10.8%. Simultaneously, the flame structure also changes. The numerical simulation that considered both gas-phase combustion and gas-solid heat transfer produced results that were in good agreement with the experiment. The results show that the change in the regression rate is a result of the magnetic force acting on the paramagnetic and diamagnetic materials. By changing the flow field, the magnetic force can change the flame shape and temperature distribution. This alters the heat exchanged between the gas and the fuel surface and thus, changes the burning rate. It was found that the burning rate of solid fuel can be adjusted regularly by applying different types of non-uniform magnetic fields, and it may be used in the solid fuel ramjet burning rate modulation.

Rapid magnetic modification of diamagnetic particulate and high aspect ratio materials

Novel method for rapid magnetic modification of diamagnetic powder and high aspect ratio materials has been developed. This procedure is based on thorough mixing of diamagnetic materials with suspensions of magnetite nano- and microparticles in highly volatile organic solvents (namely n-pentane or petroleum ether) followed by a drying step. Due to the low boiling point of the solvents used during magnetic modification, the whole process can be performed in a very short time. The prepared magnetically modified materials are stable in water for a long time, without the release of magnetic particles from the modified surface. Magnetic response of the resulting composites allows their simple separation using a permanent magnet. In addition, they have a character of composite nanozymes exhibiting peroxidase-like activity mainly due to the presence of iron oxide particles. The described method is a very efficient alternative to the previously developed magnetic modification procedures.

Modification of Diamagnetic Materials Using Magnetic Fluids

Magnetic fluids (ferrofluids) have found many important applications in various areas of biosciences, biotechnology, medicine, and environmental technology. In this review, we have summarized the relevant information dealing with a magnetic modification of diamagnetic materials using different types of ferrofluids. Special attention is focused on a magnetic modification of plant-derived biomaterials, microbial and microalgal cells, eukaryotic cells, biopolymers, inorganic materials, and organic polymers. Derivatization is usually caused by the presence of magnetic iron oxide nanoparticles within the pores of treated materials, on the materials surface or within the polymer gels. The obtained smart materials exhibit several types of responses to an external magnetic field, especially the possibility of the selective magnetic separation from difficult-to-handle environments by means of a magnetic separator. The ferrofluid-modified materials have been especially used as adsorbents, carriers, composite nanozymes or whole-cell biocatalysts.

Magnetic Processing of Diamagnetic Materials.

Currently, materials scientists and nuclear magnetic resonance spectroscopists have easy access to high magnetic fields of approximately 10 T supplied by superconducting magnets. Neodymium magnets that generate magnetic fields of approximately 1 T are readily available for laboratory use and are widely used in daily life applications, such as mobile phones and electric vehicles. Such common access to magnetic fields—unexpected 30 years ago—has helped researchers discover new magnetic phenomena and use such phenomena to process diamagnetic materials. Although diamagnetism is well known, it is only during the last 30 years that researchers have applied magnetic processing to various classes of diamagnetic materials such as ceramics, biomaterials, and polymers. The magnetic effects that we report herein are largely attributable to the magnetic force, magnetic torque, and magnetic enthalpy that in turn, directly derive from the well-defined magnetic energy. An example of a more complex magnetic effect is orientation of crystalline polymers under an applied magnetic field; researchers do not yet fully understand the crystallization mechanism. Our review largely focuses on polymeric materials. Research topics such as magnetic effect on chiral recognition are interesting yet beyond our scope.

Magnetic levitation using diamagnetism: Mechanism, applications and prospects

As a typical contact-free manipulation technique that removes friction and contamination risk, levitation has gradually become a preferred candidate for various applications. Magnetic levitation using diamagnetism, beyond Earnshaw’s theorem, is a kind of passive stable levitation that can be achieved at normal temperatures with no energy input. Appealingly, most seemingly nonmagnetic materials can be levitated in a magnetic field and can stabilize free levitation of magnetic materials. This review focuses on the fundamental principles of magnetic levitation using diamagnetism, with emphasis on its burgeoning applications. The theoretical basis associated with the magnetic levitation using diamagnetism is discussed by elucidating the characteristics of diamagnetic materials, and the key levitation mechanisms are clarified. Afterwards, state-of-the-art applications in various aspects, including sensing and measurement, actuating and micromanipulation, energy harvesting and magnetic gravity compensation, are summarized and compared. Finally, the review concludes with a brief outlook on future perspectives.

Magnetic field induced motion of water droplets and bubbles on the lubricant coated surface

Diamagnetic water droplets placed on the silicone-oil-lubricated solid surfaces were displaced by a permanent magnetic field B≅0.4T. The motion was sensitive to the hydrophobicity of the solid surface. Maximal velocities vmax≅0.1-0.2mms were registered on the silicone-oil-lubricated hydrophobic surfaces. The maximal velocities were insensitive to the volume of water droplets for the volumes in the range of 2μl<V<12μl. The maximal velocities of the droplets were also only slightly dependent on the thickness of the oil layer. A model of the motion of diamagnetic droplets driven by the permanent magnetic field is suggested. The qualitative model describes satisfactorily scaling of the experimental findings. The reported process involves purely diamagnetic materials. Motion of silicone oil bubbles driven by the magnetic field is also reported.

Study of d0 magnetism of BaF2 nanopowder after thermal and radiation exposure

Mesoporous nanocrystal BaF2 nanopowders (NPs) have been obtained with the pulsed electron beam evaporation (PEBE) technique. The transformation of the structure and morphology of BaF2 nanoparticles (NPles) induced by thermal annealing in air at temperatures of 200, 400, and 900 °C has been monitored with the XRD, SEM, and HRTEM methods. The HRTEM analysis has shown the presence of three polymorph phases (cubic, octahedral, and hexagonal) in the unannealed NP. Upon the transition into the nanoscale, diamagnetic (DM) BaF2 (in the volume state) has demonstrated both paramagnetic (PM) and ferromagnetic (FM) responses at room temperature. The thermal analysis (TA) has confirmed the strong adsorption of CO2 while synthesizingthe BaF2 NP via PEBE method and adsorption of different NOx oxides following irradiation of the BaF2 NP (in air by 700 keV electrons) The appearance of the FM contribution in the diamagnetic BaF2 NP after annealing at a temperature of 600–900 °C is likely associated with the achievement of the percolation threshold with an increase of the BaO oxide concentration. This is in agreement with the well-known theoretical predictions of d0 magnetism in N-doped (C-doped) BaO. The appearance and variations of the FM contribution to the BaF2 NP irradiated by 700 keV electrons are likely connected with an increase of the NOx oxide concentration (due to an increase of the time of electron irradiation), which confirms the hypothesis on the appearance of the FM response in solid-state N (C)-BaO solutions. The FM decrease with time is indicative of the surface character of d0 magnetism in the barium fluoride under study.

Diamagnetic Levitation Thermometer

This paper reports a diamagnetic levitation thermometer using a pyrolytic graphite (PG). The levitation height of diamagnetic materials depends on the temperature. The system is composed of a PG disc, permanent magnet for driving, non‐contact laser displacement meter, and spot heater. We evaluated the height in air and vacuum changing the temperature of the PG disc, and the disc changes its height as to be −1.49 and 1.55 µm/°C in air and vacuum, respectively. Differential thermal analysis of polystyrene is demonstrated. The potential of the diamagnetic levitation as a new principle measuring temperature changes is indicated. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Trajectory Simulation of Magnetic Particles in Dry Belt Type Magnetic Separation

Magnetic separation, which has been widely used in various industries (e.g., mineral and waste treatment) is an important part of mineral processing. In this study, the simulations of particle trajectories and the relationships between the main parameters in a dry belt-type magnetic separation system are presented. The magnetic field strength simulated by finite element analysis depended upon the vertical distance; the maximum strength was formed at a 0.31 m along the x-axis from a permanent magnet. Simulations of particle trajectories were conducted on ferromagnetic (magnetite), paramagnetic (ilmenite), and diamagnetic (quartz) materials, with variable parameters such as magnetic field strength, particle size, and degree of liberation. The simulation results showed that the key factors of magnetic susceptibility and field strength considerably affected the particle trajectory, as compared with particle size and specific gravity. Hence, the minimum magnetic field strength needed to separate magnetite and ilmenite could be obtained by the regression equation.문초록