Perpendicular Geometry Research Articles

Characterization of parametrically amplified spin wave resonances in thin YIG films

We have experimentally shown that the perpendicular pumping geometry is optimal for parametric amplification of thermal magnons, which form Spin Wave Resonances (SWR) modes in in-plane magnetized Yttrium Iron Garnet (YIG) films. Above the parametric instability threshold, the parametric SWR spectrum exhibits a second order nonlinearity: the effect of modulational instability at Continuous Wave (CW) pumping. The parametric SWR modes possess a high quality factor, Qf = 2.0 × 106 that is two orders of magnitude more than the Q factor of the Ferromagnetic Resonance (FMR) in high quality YIG films.

Structural Elucidation of N2O Clusters at Low Temperatures: Exemplary Framework Stabilized by π-Hole-Driven N···O and N···N Pnicogen Bonding Interactions.

N2O is a classic prototype, in which central nitrogen is sufficiently electropositive with a positive potential of 20 kcal mol-1 in magnitude to qualify it as a possible pnicogen. This was applied to a test with N2O clusters using ab initio calculations in association with various molecular topographic tools. The structure of the energetically dominant and N2O dimer was in favor of a perpendicular geometry, where the central nitrogen atom of the N2O submolecule assumed a near 90° angle with the adjacent N═O and/or N═N moiety, which provides the affirmation of central nitrogen as a possible π-hole-driven pnicogen. The terminal nitrogen and oxygen atoms of N2O continue to act as conventional electron donors (Lewis bases) with a negative potential. Overall, predominant π-hole-driven N···O and N···N pnicogen bonding interactions were observed to stabilize N2O clusters. Furthermore, N2O clusters (dimers and trimers) were synthesized at low temperatures in an Ar matrix using molecular beam (effusive and supersonic expansion) experiments. The geometries of these clusters were characterized by probing infrared spectroscopy with corroboration from ab initio computational methods. In addition to our previously investigated nitromethane and nitrobenzene systems, N2O also makes it to a pnicogen bonder's club with the central nitrogen as a π-hole-driven pnicogen.

A broad-band investigation of ferromagnetic resonance in exchange coupled permalloy/phthalocyanine bilayer heterostructures at room temperature

The phenomenon of ferromagnet/molecule interfacial electronic hybridization enables the possibility of modifying magnetic characteristics of downscaled systems for spintronic applications. Ferromagnetic resonance (FMR) at the nanoscale level through a coplanar waveguide (CPW) over a wide frequency range is a remarkably reliable technique for investigation of the magnetic heterostructure’s interfacial properties and their feasibility in applications as spintronic devices. Here, magnetron sputtering and organic molecular beam epitaxy methods are used to fabricate the following nanoscale heterostructures: permalloy (Py)/Fe phthalocyanine (Pc), Py/ZnPc, and Py/Cr. Magnetization dynamics of the bilayer heterostructures is investigated in a CPW by studying frequency dependence (5–50 GHz) of the resonance field and linewidth with parallel and perpendicular geometries of the static applied magnetic field, thereby providing insights into possible intrinsic and extrinsic sources of FMR damping. Planar Pc molecules at the Py layer interface are found to have the potential to contribute to magnetic stabilization based on calculated magnetic parameters. This is evidenced by the larger results of surface anisotropy of the Py/MPc bilayer heterostructures induced by exchange coupling interaction at room temperature as well as the lower values of damping constant.

Analysis of electron induced single ionisation differential cross-section of CO2 molecules in different kinematics

Theoretical investigations of electron-impact ionisation for carbon dioxide (CO2) in low to intermediate energy ranges are presented. In addition to the energy range, we have estimated triple differential cross-section (TDCS) in coplanar and perpendicular plane geometry. We have calculated the TDCS for electron impact using the modified distorted wave formalism up to the second order. Post-collision interaction effects have also been introduced to describe the collision dynamics accurately. There is a good correlation between the distorted-wave Born approximation results and the experimental results in terms of forward and backward scattering regions.

Electron vortices generation of photoelectron of H2+ by counter-rotating circularly polarized attosecond pulses

Molecular-frame photoelectron momentum distributions (MF-PMDs) of an H2+ molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrödinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counter-rotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distance-dependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs.

Commissioning of a RayStation structure template for the iBEAM evo Couchtop.

Accurate radiotherapy treatment planning requires attenuation through the treatment couch to be accounted for in dose calculation. This is commonly performed by using contouring tools to add a virtual structure in the shape of the treatment couch and assigning the preferred absorption properties. The RayStation treatment planning system (TPS) allows users to assign a material that comprises both an elemental structure and a physical density. The selection of such parameters should be made so that modelled attenuation through the couch closely matches measured data. When these measurements involve the use of plastic phantoms and rotational beams, the validity of the data is dependent upon aspects of TPS and linear accelerator performance that can be difficult to quantify. A fundamental measure of couch attenuation using an ionisation chamber in water and perpendicular beam geometry that required no gantry movement was implemented to eliminate the identified uncertainties. This data was used to determine the combination of elemental composition and density assigned to a modelled couch structure that provided the most accurate representation of beam attenuation in this simple geometry. The preferred material was then validated using a cylindrical phantom and rotational beams. The findings were equivalent between the static gantry with water phantom and rotating gantry with cylindrical phantom. Of the elemental compositions investigated, it was possible to achieve suitable agreement with the measured data for each option provided the density was optimised. Choice of the elemental composition was not observed to be an important factor in achieving a good model.

Triply differential cross sections for electron and positron impact on methane.

We here report theoretical triply differential cross sections (TDCS) for 250eV electron and positron impact ionization of the methane molecule calculated within the second-order distorted-wave Born approximation (DWBA2) for various momentum transfer conditions. The experimental data taken from Işık et al. [J. Phys. B: At., Mol. Opt. Phys. 49, 065203 (2016)] will be compared with the current theoretical predictions as well as molecular three body distorted wave (M3DW) approximation and generalized Sturmian function (GSF) theoretical models in a non-coplanar geometry. In the low analyzer scattering plane, the results obtained within the DWBA2 theory show better agreement with the experimental results compared to the GSF results. The M3DW results also exhibit agreement with the experimental results, in particular in the perpendicular plane geometry. Furthermore, significant differences between electron and positron TDCS were observed.

Axial Chirality in Alkylidene‐Cyclic Molecules

AbstractAxial chirality is an interesting stereoisomeric phenomenon in organic chemistry and a key structural feature of several organic compounds. Atropisomers such as biaryls, anilides and diaryl ethers are one type of axially chiral compounds, whose axial chirality is resulted from rotationally blocked single bond. Allenes, spiranes and alkylidenecycloalkanes are another type of axially chiral compounds and their axial chirality come from the perpendicular geometry of two pairs of substituents. The axial chirality in atropisomers, allenes and spiranes has been widely investigated and well developed, while the similar chirality in alkylidene‐cyclic molecules gained very limited attentions. This concept focuses on summarizing recent advances of axial chirality in alkylidene‐cyclic molecules and arouses the research interests to this promising field.

Dimensional crossover on multileg attractive- U Hubbard ladders

We study the ground state properties of a polarized two-component Fermi gas on multileg attractive-$U$ Hubbard ladders. Using exact diagonalization and density matrix renormalization group method simulations, we construct grand canonical phase diagrams for ladder widths of up to $W=5$ and varying perpendicular geometries, characterizing the quasi-one-dimensional regime of the dimensional crossover. We unveil a multicritical point marking the onset of partial polarization in those phase diagrams, a candidate regime of finite-momentum pairing. We compare our findings with recent experimental and theoretical studies of quasi-one-dimensional polarized Fermi gases.

Graphene Oxide-BODIPY Conjugates as Highly Fluorescent Materials.

Covalent functionalization of graphene oxide (GO) with boron dipyrromethenes (BODIPYs) was achieved through a facile synthesis, affording two different GO-BODIPY conjugates where the main difference lies in the nature of the spacer and the type of bonds between the two components. The use of a long but flexible spacer afforded strong electronic GO-BODIPY interactions in the ground state. This drastically altered the light absorption of the BODIPY structure and impeded its selective excitation. In contrast, the utilisation of a short, but rigid spacer based on boronic esters resulted in a perpendicular geometry of the phenyl boronic acid BODIPY (PBA-BODIPY) with respect to the GO plane, which enables only minor electronic GO-BODIPY interactions in the ground state. In this case, selective excitation of PBA-BODIPY was easily achieved, allowing to investigate the excited state interactions. A quantitative ultrafast energy transfer from PBA-BODIPY to GO was observed. Furthermore, due to the reversible dynamic nature of the covalent GO-PBA-BODIPY linkage, some PBA-BODIPY is free in solution and, hence, not quenched from GO. This resulted in a weak, but detectable fluorescence from the PBA-BODIPY that will allow to exploit GO-PBA-BODIPY for slow release and imaging purposes.

High-order harmonic generation in orthogonal IR and XUV pulses: XUV-initiated channel separation and polarization control

Single-atom high-order harmonic generation (HHG) induced by an intense linearly polarized infrared (IR) field and assisted by a perturbative extreme ultraviolet (XUV) short pulse with linear polarization is analyzed in perpendicular geometry. It is shown that for the case of the initial $p$ state, the two independent projections of the laser-induced dipole are formed by two independent physical channels, which are responsible for IR-induced HHG and XUV-initiated HHG. This property of the laser-induced dipole is utilized for polarization control of the generated radiation. An alternative scheme for studying XUV-initiated HHG is proposed.

"Medium-ring" strategy enables high-performance narrowband pure-blue multi-resonance emitters: boost provided by a unique perpendicular geometry.

The introduction of a heptagonal tribenzo[b,d,f]azepine (TBA) donor onto BCz-BN enabled the development of a pure-blue narrowband emitter, TBA-BCz-BN, and induced a significant blue shift of emission from 483 nm to 468 nm and a decrease in the singlet-triplet energy gap from 0.17 eV to 0.14 eV. The corresponding TBA-BCz-BN-based OLED exhibited a high external quantum efficiency of 30.8%.

Using Apparent Electrical Conductivity to Delineate Field Variation in an Agroforestry System in the Ozark Highlands

Greater adoption and better management of spatially complex, conservation systems such as agroforestry (AF) are dependent on determining methods suitable for delineating in-field variability. However, no work has been conducted using repeated electromagnetic induction (EMI) or apparent electrical conductivity (ECa) surveys in AF systems within the Ozark Highlands of northwest Arkansas. As a result, objectives were to (i) evaluate spatiotemporal ECa variability; (ii) identify ECa-derived soil management zones (SMZs); (iii) establish correlations among ECa survey data and in situ, soil-sensor volumetric water content, sentential site soil-sample EC, and gravimetric water content and pH; and (iv) determine the optimum frequency at which ECa surveys could be conducted to capture temporal changes in field variability. Monthly ECa surveys were conducted between August 2020 and July 2021 at a 4.25 ha AF site in Fayetteville, Arkansas. The overall mean perpendicular geometry (PRP) and horizontal coplanar geometry (HCP) ECa ranged from 1.8 to 18.0 and 3.1 to 25.8 mS m−1, respectively, and the overall mean HCP ECa was 67% greater than the mean PRP ECa. The largest measured ECa values occurred within the local drainage way or areas of potential groundwater movement, and the smallest measured ECa values occurred within areas with decreased effective soil depth and increased coarse fragments. The PRP and HCP mean ECa, standard deviation (SD), and coefficient of variation (CV) were unaffected (p > 0.05) by either the weather or growing/non-growing season. K-means clustering delineated three precision SMZs that were reflective of areas with similar ECa and ECa variability. Results from this study provided valuable information regarding the application of ECa surveys to quantify small-scale changes in soil properties and delineate SMZs in highly variable AF systems.

Molecular design of blue thermally activated delayed fluorescent emitters for high efficiency solution processable OLED via an intramolecular locking strategy

Realizing high-efficiency blue emission in solution processable organic light-emitting diode (OLED) with thermally activated delayed fluorescent (TADF) emitters is still a big challenge. To suppress the non-radiative process in TADF emitters, compound DPS-BF-Ac featuring a donor-π-acceptor skeleton is prepared via intramolecular cyclization, in which diphenylsulfone (DPS), acridine (Ac) and furan derivatives are regarded as the donor, acceptor and π linker, respectively. Then, compounds DPS-Ph-Ac, DPS-OMe-Ac and DPS-OH-Ac with different π linkers are investigated to further explore the molecular structure–property relationship. All compounds show promising blue emission with a clear TADF character. Single crystal analysis demonstrate that compound DPS-BF-Ac possesses almost a perpendicular geometry between donor and acceptor groups and expanded molecular rigidity, leading to a smaller singlet–triplet energy difference and greatly improved emission efficiency. A remarkable external quantum efficiency (EQEmax) of ∼ 25 % is achieved for the DPS-BF-Ac based solution OLED, concomitant with the emission peak at ∼ 480 nm. Using DPS-BF-Ac and PO-01 as the blue and red dopant, respectively, the white OLED exhibits an EQEmax of ∼ 29 %. This research shows that intramolecular cyclization is an effective strategy for designing high efficiency solution-processable blue TADF emitter.

Perpendicular full switching of chiral antiferromagnetic order by current.

Electrical control of a magnetic state of matter lays the foundation for information technologies and for understanding of spintronic phenomena. Spin-orbit torque provides an efficient mechanism for the electrical manipulation of magnetic orders1-11. In particular, spin-orbit torque switching of perpendicular magnetization in nanoscale ferromagnetic bits has enabled the development of stable, reliable and low-power memories and computation12-14. Likewise, for antiferromagnetic spintronics, electrical bidirectional switching of an antiferromagnetic order in a perpendicular geometry may have huge impacts, given its potential advantage for high-density integration and ultrafast operation15,16. Here we report the experimental realization of perpendicular and full spin-orbit torque switching of an antiferromagnetic binary state. We use the chiral antiferromagnet Mn3Sn (ref. 17), which exhibits the magnetization-free anomalous Hall effect owing to a ferroic order of a cluster magnetic octupole hosted in its chiral antiferromagnetic state18. We fabricate heavy-metal/Mn3Sn heterostructures by molecular beam epitaxy and introduce perpendicular magnetic anisotropy of the octupole using an epitaxial in-plane tensile strain. By using the anomalous Hall effect as the readout, we demonstrate 100 per cent switching of the perpendicular octupole polarization in a 30-nanometre-thick Mn3Sn film with a small critical current density of less than 15 megaamperes per square centimetre. Our theory reveals that the perpendicular geometry between the polarization directions of current-induced spin accumulation and of the octupole persistently maximizes the spin-orbit torque efficiency during the deterministic bidirectional switching process. Our work provides a significant basis for antiferromagnetic spintronics.

Adsorption of Benzene-1,4-diol, 3-Methyl-1,2-cyclopentanedione and 2,6-Dimethoxyphenol on aluminium (1 1 1) plane using density functional theory calculations

The corrosion inhibitive actions of a few potential organic molecules extracted from rice husk bio-oil, namely benzene-1,4-diol, 3-methyl-1,2-cyclopentanedione, and 2,6-dimethoxyphenol, were investigated using first-principle calculation. Adsorption of these molecules on the aluminium (111) plane was simulated to unravel the inhibitor-surface bonding mechanism using a density functional theory with different adsorption sites and molecule geometry orientations. The electronic properties of the adsorption system also revealed the bonding mechanism and the different bonding characters between the three molecules. Based on the calculated adsorption parameters and electronic properties between inhibitor and surface atom, the 3-methyl-1,2-cyclopentanedione was discovered to be chemisorbed in both perpendicular and parallel geometry. It is pointed out that the π-system and oxygen lone pairs of 3-methyl-1,2-cyclopentanedione are rather important. Meanwhile, the benzene-1,4-diol and 2,6-dimethoxyphenol molecules were physisorbed in both geometries, andthe bond lengths between oxygen and aluminium atoms are longer than the covalent radii of oxygen-aluminium. Finally, 3-Methyl-1,2-cyclopentanedione was identified as the most effective corrosion inhibitor to substantially reduce corrosion due to strong interaction with the aluminium surface.

Stellar Companions to TESS Objects of Interest: A Test of Planet–Companion Alignment

Abstract We present a catalog of stellar companions to host stars of Transiting Exoplanet Survey Satellite Objects of Interest (TOIs) identified from a marginalized likelihood ratio test that incorporates astrometric data from the Gaia Early Data Release 3 catalog (EDR3). The likelihood ratio is computed using a probabilistic model that incorporates parallax and proper-motion covariances and marginalizes the distances and 3D velocities of stars in order to identify comoving stellar pairs. We find 172 comoving companions to 170 non-false-positive TOI hosts, consisting of 168 systems with two stars and 2 systems with three stars. Among the 170 TOI hosts, 54 harbor confirmed planets that span a wide range of system architectures. We conduct an investigation of the mutual inclinations between the stellar companion and planetary orbits using Gaia EDR3, which is possible because transiting exoplanets must orbit within the line of sight; thus, stellar companion kinematics can constrain mutual inclinations. While the statistical significance of the current sample is weak, we find that 73 − 20 + 14 % of systems with Kepler-like architectures (R P ≤ 4 R ⊕ and a < 1 au) appear to favor a nonisotropic orientation between the planetary and companion orbits with a typical mutual inclination α of 35° ± 24°. In contrast, 65 − 35 + 20 % of systems with close-in giants (P < 10 days and R P > 4 R ⊕) favor a perpendicular geometry (α = 89° ± 21°) between the planet and companion. Moreover, the close-in giants with large stellar obliquities (planet–host misalignment) are also those that favor significant planet–companion misalignment.

Exploring Orthogonality between Halogen and Hydrogen Bonding Involving Benzene.

The concept of orthogonality between halogen and hydrogen bonding, brought out by Ho and coworkers some years ago, has become a widely accepted idea within the chemists’ community. While the original work was based on a common carbonyl oxygen as acceptor for both interactions, we explore here, by means of M06-2X, M11, ωB97X, and ωB97XD/aug-cc-PVTZ DFT calculations, the interdependence of halogen and hydrogen bonding with a shared π-electron system of benzene. The donor groups (specifically NCBr and H2O) were placed on either or the same side of the ring, according to a double T-shaped or a perpendicular geometry, respectively. The results demonstrate that the two interactions with benzene are not strictly independent on each other, therefore outlining that the orthogonality between halogen and hydrogen bonding, intended as energetical independence between the two interactions, should be carefully evaluated according to the specific acceptor group.

Laser-induced two-step demagnetization process study in Ni–Mn–Sn Heusler alloy film

The ultrafast magnetization dynamic processes are investigated in a wide time scale range for different laser pump fluences in Ni- and Mn-rich Heusler alloy film of Ni54.3Mn31.9Sn13.8 composition using time-resolved magneto-optical Kerr effect (TR-MOKE) in perpendicular magnetic field geometry. For all fluences used, two distinct types of magnetization dynamics of different time scales: ultrafast up to 2 picoseconds and slower from 2 ps to hundreds of ps, were observed. The description of the two-step de- and remagnetization processes was performed in the frame of modified model developed, based on the microscopic three-temperature model (M3TM). The model is based on the assumption that two magnetic sublattices of the Heusler alloy which are weakly exchange coupled due to Curie temperature proximity are responsible for the fast and slow magnetization dynamics. It is demonstrated excellent agreement of the model prediction with experimental data for all the fluences used. It is shown that the values of model parameters determined — demagnetization rates R and spin-flip probabilities asf for one sublattice are of the order reported for the Ni film. It has been found that R parameter value for the second sublattice related to Mn site is over two orders, and asf is up to one order of magnitude lower than in Ni site. It is shown that strong reduction of the spin-flip probability and electron–phonon coupling, and large magnetic moment in the Mn sublattice as compared to the Ni one is the cause of the observed demagnetization slowing down effect in the Heusler alloy studied.

First‐principles based theoretical investigation of the adsorption of alkanethiols on the iron surface: A DFT-D3 study

The search for novel corrosion inhibitors is a never-ending and challenging task. Computational studies are fundamental to assessing the interaction of inhibitor molecules with metals, thus opening the way to design new inhibitors with specific characteristics. Herein, first-principles DFT-D3 calculations were performed to simulate the bonding of three alkanethiols, namely 11-mercaptoundecanoic acid (MDA), decanethiol (DT), hexanethiol (HT) with the iron surface Fe(110). The interaction energies obtained from different adsorption systems predicted this adsorption strength: MDA > DT > HT. The perpendicular adsorption geometries were found to be more stable than other adsorption modes. However, all adsorption configurations showed covalent interactions between sulfur atom and iron surface. Electron density difference (EDD) plots and projected density of states (PDOS) further confirmed the electron-donation and back-donation synergic interactions between interactive systems. This study showed that alkanethiols with a long carbon chain and an end-functional group had increased charge transfer and bonding with the bare iron surface, i.e., Fe(110).