Perpendicular Magnetic Field Research Articles

Design of Experiments Informed Investigation of Magnetic Field Assisted Nickel Electroplating on Copper

Abstract Nickel coatings have demonstrated significant benefits in protecting copper from oxidation and fouling, thereby enhancing the longevity of copper-based components. This study employed an electroplating apparatus featuring a Watts bath and copper electrode to investigate the impact of flowing electrolyte, both with and without an applied magnetic field, on the interfacial characteristics of nickel-coated copper surfaces. The findings reveal the relationship between current density and deposition thickness. The application of a perpendicular magnetic field and increase in current density generally increased coating thickness to 0.2 ?m from 0.05 ?m, with the most pronounced effects at moderate flow rates and narrower gaps; however, at the highest flow rate and widest gap, deposition thickness diminished due to the divergence of magnetic field lines. Design of Experiments analysis revealed the magnetic field homogeneously improved surface roughness uniformity compared to other variables. Lower current densities produced smoother surfaces, while magnetically-assisted electroplating yielded consistent roughness values even at higher current densities. Exposure to the magnetic field improved wettability, evidenced by decreased contact angles. This enhancement is attributed to the alignment of nickel particles during deposition, facilitating a transition from the Cassie-Baxter to the Wenzel wetting state. Notably, thicker deposits were observed at lower flow rates and narrower electrode gaps, suggesting significant influence of gas bubble dynamics on the deposition process. These findings provide insights into the complex interplay between electrochemical reactions, hydrodynamics, and magnetic fields in nickel electrodeposition, with implications for optimizing coating.

Dynamics and energy dissipation of collisional blast waves in a perpendicular magnetic field

We experimentally investigate the evolution and dynamics of laser-produced collisional blast waves (BW) under the influence of a perpendicular magnetic field up to 20 T. We show that an external magnetic field causes the BW to diverge from the Taylor–Sedov solution while also impacting its structural morphology. We notably explore the significance of various magnetohydrodynamic (MHD) processes occurring on scales similar to the width of the BW front by comparing their characteristic lengths to it and demonstrate that the downstream plasma's transition from being super- to sub-magnetosonic plays a pivotal role in the overall structure. Our results show that multiple MHD effects can contribute to shaping a magnetized BW, illustrating the complexity of the underlying physics.

Perturbing Pentalene: Aromaticity and Antiaromaticity in a Non-alternant Polycyclic Aromatic Hydrocarbon and BN-heteroanalogues.

Pentalene (C8H6) and NN- and BB-bridged heterocyclic analogues (BN)4H6, derived by replacement of CC pairs with BN, are taken as paradigms for tuning of ring-current (anti)aromaticity by variation of πcharge, electronegativity and substitution pattern. Ab initiocalculation of maps for the π current density induced in these model systems by a perpendicular external magnetic field exhibits the full range of tropicity, from diatropic aromatic to nonaromatic to paratropic antiaromatic, with a ready rationalisation in terms of an orbital model. Further calculations on systems of varying charge in which these motifs are embedded in extended PAH systems with naphthalene and phenanthrene 'clamps'show promise for switching between current patterns and related opto-electronic properties. Particular sensitivity to charge is found for the experimentally accessible NN-bridged heteropentalene hybrids.

Controlled Capture of Magnetic Nanoparticles from Microfluidic Flows by Ferromagnetic Antidot and Dot Nanostructures.

The capture of magnetic nanoparticles (MNPs) is essential in the separation and detection of MNPs for applications such as magnetic biosensing. The sensitivity of magnetic biosensors inherently depends upon the distribution of captured MNPs within the sensing area. We previously demonstrated that the distribution of MNPs captured from evaporating droplets by ferromagnetic antidot nanostructures can be controlled via an external magnetic field. In this paper, we demonstrate the capture of magnetic nanoparticles from a microfluidic flow by four variants of antidot array nanostructures etched into 30 nm thick Permalloy films. The nanostructures were exposed to 130 nm MNP clusters passing through microfluidic channels with square cross-sections of 400 μm × 400 μm. In the presence of a parallel magnetic field, up to 83.1% of nanoparticles were captured inside the antidot holes. Significantly higher proportions of nanoparticles were captured within the antidots from the flow than when applying the nanoparticles via droplets. In the parallel field configuration, MNPs can be focused into the regularly spaced antidot indents in the nanostructure, which may be useful when detecting or observing MNPs and their conjugates. Conversely, up to 84% of MNPs were caught outside of antidots under a perpendicular magnetic field. Antidot nanostructures under this perpendicular configuration show potential for MNP filtration applications.

Stabilization of a two-dimensional quantum electron solid in perpendicular magnetic fields

Stabilization of a two-dimensional quantum electron solid in perpendicular magnetic fields

Observation and Simulation of Chorus Waves in Middle Magnetotail (r > 20 RE)

AbstractWhistler‐mode chorus waves, characterized by repetitive frequency‐chirping elements, have traditionally been considered to be confined to near‐planet dipolar magnetic fields. In contrast to this long‐held belief, here we present the first observation of whistler‐mode chorus waves in the middle magnetotail beyond 20 RE from Earth, based on MMS measurements. These rising‐tone chorus waves exhibit significantly higher chirping rates compared to those in radiation belts. Using the PIC simulation, we demonstrate these chorus waves can be locally generated, driven by perpendicular flux anisotropy and magnetic field inhomogeneity inside the pileup region. This region, resembling a magnetic bottle, shares shape similarities with the inner magnetosphere but provides a much greater inhomogeneity, resulting in higher chirping rates. These discoveries provide new inspirations for the generation of chorus waves and may lead to new insights into their behavior in space.

Discharge and Gas Parameters Optimization for Toluene Degradation in a Perpendicular Magnetic Field‐Assisted Dielectric Barrier Discharge Reactor

ABSTRACTIn this study, we employed a nanosecond‐pulsed gear‐cylinder dielectric barrier discharge (DBD) assisted by a perpendicular magnetic field (MF) for toluene degradation. The effects of key discharge and gas parameters, as well as their optimal combinations with the perpendicular MF, on toluene degradation were systematically investigated. The results indicated that the maximum toluene degradation efficiency was achieved under conditions of short pulse rising times and widths, low gas flow velocities, and minimal oxygen concentrations. This optimal performance was attributed to three main factors: high mean electron energy, the generation of appropriate active oxygen species, and an extended residence time for plasma‐toluene molecule interactions. Furthermore, by meticulously adjusting the operational parameters, augmenting the number of magnetized energetic electrons in the perpendicular MF, and intensifying the ionization process, we observed a notable enhancement in both discharge intensity and toluene degradation efficiency.

Unveiling the phases of bulk ZrTe5through magnetotransport phenomena.

We present a straightforward method which may greatly simplify and lower the threshold for determining the phase of the relatively enigmatic quantum material-ZrTe5. In this study, without directly probing the band structure, we identify the topological phase of the three-dimensional (3D) bulk ZrTe5crystal solely through low-temperature electrical and magnetotransport measurements. A two-dimensional (2D) weak antilocalization (WAL) effect was observed in our bulk ZrTe5crystal, along with clear Shubnikov-de Haas oscillations. The large prefactorαderived from WAL analyses indicates the presence of multiple conducting channels in the bulk ZrTe5crystal, where each channel is associated with individual 2D ZrTe5layers. It is the largeαvalue provides insights into the topological Dirac semimetal phase inherent to our ZrTe5crystal. Additionally, we analyze the pronounced linear magnetoresistance and saturation behavior under a perpendicular magnetic field. Our results suggest that bulk ZrTe5crystals, which exhibit unique layered transport features, serve as a promising platform for further research in quantum phases and transitions in 3D quantum systems.

Remagnetization processes of uniaxial ferromagnetic films with spatially modified parameters

The study examines the behavior of vortex-like magnetic inhomogeneities that arise in a ferromagnetic disk with spatially modulated uniaxial anisotropy under magnetic fields of varying orientations. The research identifies the characteristic remagnetization stages of the vortex-like inhomogeneities formed in the region of the defect. critical fields of their rearrangement are found and an explanation is given for the difference in the behavior of these inhomogeneities in perpendicular and planar magnetic fields. The effect of the helicity of the magnetic skyrmion localized on the defect on its remagnetization process in the planar field is revealed.

Structural and Optical Anomalies in Thin Films Grown in a Magnetic Field by Electron‐Assisted Vacuum Deposition of PTFE

AbstractPolytetrafluoroethylene (PTFE) films are deposited in parallel and perpendicular magnetic fields (MF) by electron‐enhanced vacuum deposition (EVD) and EVD + low‐temperature plasma (LTP) methods. The structure, morphology, and nanomechanical properties of the films are studied by infrared spectroscopy (IRS), atomic force microscopy (AFM), and spectroscopic ellipsometry. The structure of the thicker films is closer to that of bulk PTFE than that of thin films. The films' crystallinity and surface roughness are higher than those deposited without MF. The birefringence of the refractive index (n) of the films deposited in the MF is inverse to the anisotropy of the n of the films deposited without MF. The hardness of the films is close to that of bulk PTFE.

Instability of motion of relativistic charged particles in non-uniform stationary electromagnetic fields

It is well established that a sufficiently large gradient of the electric field causes instability of the motion of charged particles in mutually perpendicular electric and magnetic fields. This instability leads to an effective energization of the particles by electrostatic electric fields. The minimum value of the electric field gradient required for this instability to occur for non-relativistic particles depends on the strength of the magnetic field but is independent of both the particle velocity and the local electric field strength. This paper describes an instability caused by non-uniformity of the electric field for relativistic particles and demonstrates that its threshold in the relativistic case depends, in addition to the magnetic field intensity, on the speed of the particle and the local strength of the electric field. Larger particle speeds and larger electric fields reduce the gradient of the electric field required to make the particle motion unstable.

Rheology and magnetorheology of ferrofluid emulsions: Insights into formulation and stability

The integration of surfactants and nanoparticles in emulsion formulations has attracted significant attention due to their potential synergistic effects, improving stability and enabling the development of stimuli-responsive materials. The objective of this study was to investigate the stability, bulk rheological, and magnetorheological properties of oil in water (o/w) emulsions, composed of Fe3O4 kerosene-based ferrofluids dispersed in surfactant solutions (hexadecylpyridinium chloride, and nonylphenol polyethoxylate—ethylene oxide = 40, known as Tergitol NP-40), as a function of concentration and nature of the emulsifying agents. The results demonstrated the formation of stable systems (>2 months), featuring an average droplet size below 4 μm, with the primary stabilization mechanism attributed to the reduction of interfacial tension by surfactant activity. The emulsions exhibited shear thinning and viscoelastic solid-like behavior, which were enhanced by increasing the concentrations of both emulsifiers. Emulsions stabilized with hexadecylpyridinium exhibited a higher structural rigidity, with dynamic moduli an order of magnitude higher than Tergitol formulations. In the presence of a perpendicular magnetic field, it was demonstrated that incorporating ferrofluid as a dispersed phase in an o/w emulsion potentiates the magnetoviscous effect, compared to that observed with neat ferrofluid at the same concentration. A maximum relative increase in viscosity of up to 17-fold was observed in emulsions stabilized with 2.5 w/v% of hexadecylpyridinium and 10 000 ppm of nanoparticles when exposed to a linearly increasing magnetic field up to 796.73 mT at 1 s−1. The observed magnetoviscous effect remained reproducible for up to one year after formulation, highlighting the potential of these systems for multiple applications.

Disorder and spin-orbit coupling in the integer quantum Hall effect

The physics of two-dimensional electron gas (2DEG) in the presence of a perpendicular magnetic field, disordered potential, and spin-orbit coupling (SOC) is very rich. It touches upon numerous fundamental concepts such as Anderson localization, the integer quantum Hall effect, and random matrix ensembles (Gaussian, unitary, and symplectic). At strong magnetic field the system is extensively studied. It is characterized by isolated Landau levels wherein the energy is linear with the magnetic field and the corresponding wave functions are extended, while between two Landau levels, the corresponding wave functions are localized. In most cases, for strong magnetic field, pertinent calculations are based on the projection of a single Landau level. The first topic to be discussed below is the Anderson localization at weak magnetic field and strong, albeit uniform SOC. In fact, the physics at weak magnetic field seems to be even richer than that at strong magnetic field. Indeed, projection on a single Landau level is not justified, since the energy distance between adjacent levels compares with the strength of disorder and the SOC energy. The second topic to be discussed below is the Anderson localization in a strong magnetic field and with random SOC.

The DKP equation for a spin-1 boson in a magnetic field and the two-photon Jaynes–Cummings model

The DKP equation for a spin-1 boson in a magnetic field and the two-photon Jaynes–Cummings model

Quantum Griffiths Singularity in a Three-Dimensional Superconductor to Anderson Critical Insulator Transition.

Disorder is ubiquitous in real materials and can have dramatic effects on quantum phase transitions. Originating from the disorder enhanced quantum fluctuation, quantum Griffiths singularity (QGS) has been revealed as a universal phenomenon in quantum criticality of low-dimensional superconductors. However, due to the weak fluctuation effect, QGS is very challenging to detect experimentally in three-dimensional (3D) superconducting systems. Here we report the discovery of QGS associated with the quantum phase transition from 3D superconductor to Anderson critical insulator in a spinel oxide MgTi_{2}O_{4} (MTO). Under both perpendicular and parallel magnetic field, the dynamical critical exponent diverges when approaching the quantum critical point, demonstrating the existence of 3D QGS. Among 3D superconductors, MTO shows a relatively strong fluctuation effect featured as a wide superconducting transition region. The enhanced fluctuation, which may arise from the mobility edge of Anderson localization, finally leads to the occurrence of 3D quantum phase transition and QGS. Our findings offer a new perspective to understand quantum phase transitions in strongly disordered 3D systems.

Evidence for correlated electron pairs and triplets in quantum Hall interferometers

The pairing of electrons is ubiquitous in electronic systems featuring attractive inter–electron interactions, as exemplified in superconductors. Counterintuitively, it can also be mediated in certain circumstances by the repulsive Coulomb interaction alone. Quantum Hall (QH) Fabry–Pérot interferometers (FPIs) tailored in a two–dimensional electron gas under a perpendicular magnetic field have been argued to exhibit such an unusual electron pairing, seemingly without attractive interactions. Here, we show evidence in graphene QH FPIs, revealing not only a similar electron pairing at bulk filling factor νB = 2, but also an unforeseen emergence of electron tripling characterized by a fractional Aharonov–Bohm flux period of h/3e (h is the Planck constant and e the electron charge) at νB = 3. Leveraging plunger–gate spectroscopy, we demonstrate that electron pairing (tripling) involves correlated charge transport on two (three) entangled QH edge channels. This spectroscopy indicates a quantum interference flux periodicity determined by the sum of the phases acquired by the distinct QH edge channels having slightly different interfering areas. Phase jumps observed in the pajama maps can be accounted for by the frequency beating between pairing/tripling modes and the outer interfering edge.

Spin-valley locked excited states spectroscopy in a one-particle bilayer graphene quantum dot

Current semiconductor qubits rely either on the spin or on the charge degree of freedom to encode quantum information. By contrast, in bilayer graphene the valley degree of freedom, stemming from the crystal lattice symmetry, is a robust quantum number that can therefore be harnessed for this purpose. The simplest implementation of a valley qubit would rely on two states with opposite valleys as in the case of a single-carrier bilayer graphene quantum dot immersed in a small perpendicular magnetic field (B⊥ ≲ 100 mT). However, the single-carrier quantum dot excited states spectrum has not been resolved to date in the relevant magnetic field range. Here, we fill this gap, by measuring the parallel and perpendicular magnetic field dependence of this spectrum with an unprecedented resolution of 4 μeV. We use a time-resolved charge detection technique that gives us access to individual tunnel events. Our results come as a direct verification of the predicted spectrum and establish a new upper-bound on inter-valley mixing, equal to our energy resolution. Our charge detection technique opens the door to measuring the relaxation time of a valley qubit in a single-carrier bilayer graphene quantum dot.

Uncovering bound states in the continuum in InSb nanowire networks

Uncovering bound states in the continuum in InSb nanowire networks

Quantum Machines Using Cu3$\mathrm{Cu}_{3}$‐Like Compounds Modeled by Heisenberg Antiferromagnetic in a Triangular Ring

AbstractA theoretical study of an antiferromagnetically coupled spin system, specifically , characterized by a slightly distorted equilateral triangle configuration is presented. Using the Heisenberg model with exchange and Dzyaloshinskii–Moriya interactions, g‐factors, and an external magnetic field, three quantum machines are investigated using this system as the working substance, assuming reversible processes. For the magnetocaloric effect (MCE) is significant at low temperatures (1K) under a perpendicular magnetic field (). Although only the compound is considered, since the compound behaves quite similarly. How MCE influences the Carnot machine, which operates as a heat engine or refrigerator when varying the external magnetic field is analyzed. In contrast, the Otto and Stirling machines can operate as heat engines, refrigerators, heaters, or thermal accelerators, depending on the magnetic field intensity. The results indicate that enhanced MCE broadens the operating regions for these machines, with the Otto and Stirling machines primarily functioning as refrigerators and accelerators. The corresponding thermal efficiencies are also discussed for all operating modes.

Investigation of thermodynamic properties of bilayer graphene under dual gating with perpendicular magnetic field

Investigation of thermodynamic properties of bilayer graphene under dual gating with perpendicular magnetic field