Effective Spin Research Articles

A nuclear configuration interaction approach to study nuclear spin effects: an application to ortho- and para-3 He2 @C60.

We introduce a non-orthogonal configuration interaction approach to investigate nuclear quantum effects on energies and densities of confined fermionic nuclei. The Hamiltonian employed draws parallels between confined systems and many-electron atoms, where effective non-Coulombic potentials represent the interactions of the trapped particles. One advantage of this method is its generality, as it offers the potential to study the nuclear quantum effects of various confined species affected by effective isotropic or anisotropic potentials. As a first application, we analyze the quantum states of two 3 He atoms encapsulated in C60 . At the Hartree-Fock level, we observe the breaking of spin and spatial symmetries. To ensure wavefunctions with the correct symmetries, we mix the broken-symmetry Hartree-Fock states within the non-orthogonal configuration interaction expansion. Our proposed approach predicts singly and triply degenerate ground states for the singlet (para-3 He2 @C60 ) and triplet (ortho-3 He2 @C60 ) nuclear spin configurations, respectively. The ortho-3 He2 @C60 ground state is 5.69 cm-1 higher in energy than the para-3 He2 @C60 ground state. The nuclear densities obtained for these states exhibit the icosahedral symmetry of the C60 embedding potential. Importantly, our calculated energies for the lowest 85 states are in close agreement with perturbation theory results based on a harmonic oscillator plus rigid rotor model of 3 He2 @C60 .

Enhanced effective spin Hall efficiency contributed by the extrinsic spin Hall effect in Pt1- x Ta x /CoFeB structures

High effective spin Hall efficiency and low magnetic damping constant are essential to achieve efficient spin-charge conversion for energy-efficient spintronic devices. We report the measurements of effective spin Hall efficiency and magnetic damping constant of Pt1- x Ta x /CoFeB structures using spin-torque ferromagnetic resonance (ST-FMR) techniques. With the increase of Ta content, the spin Hall efficiency increases and peaks x = 0.15 with the value of θSHeff=0.35 , before decreases for further Ta content. This non-monotonic variation is attributed to the interaction between the contribution of the extrinsic skew scattering mechanism and the spin-orbit coupling (SOC). The weakening of the SOC in the Pt1-x Ta x layer leads to a decrease in the effective magnetic damping constant with increasing Ta concentration. High-temperature ST-FMR measurements confirm the influence of the Ta concentration on the spin Hall effect and magnetic damping mechanism. Additionally, the decrease in spin mixing conductance and the increase in spin diffusion length leads to a decrease in the interfacial spin transparency.

Generalised Jeffery's equations for rapidly spinning particles. Part 1. Spheroids

The observed behaviour of passive objects in simple flows can be surprisingly intricate, and is complicated further by object activity. Inspired by the motility of bacterial swimmers, in this two-part study we examine the three-dimensional motion of rigid active particles in shear Stokes flow, focusing on bodies that induce rapid rotation as part of their activity. In Part 1 we develop a multiscale framework to investigate these emergent dynamics and apply it to simple spheroidal objects. In Part 2 (Dalwadi et al., J. Fluid Mech., vol. 979, 2024, A2) we apply our framework to understand the emergent dynamics of more complex shapes; helicoidal objects with chirality. Via a multiple scales asymptotic analysis for nonlinear systems, we systematically derive emergent equations of motion for long-term trajectories that explicitly account for the strong (leading-order) effects of fast spinning. Supported by numerical examples, we constructively link these effective dynamics to the well-known Jeffery's orbits for passive spheroids, deriving an explicit closed-form expression for the effective shape of the active particle, broadening the scope of Jeffery's seminal study to spinning spheroids.

Compressing the atomic cloud in a matter-wave stripe soliton

We consider an attractive quasi-one dimensional spin-orbit coupled Bose–Einstein condensate (SOC BEC) confined in a periodic potential produced by the combination of linear and nonlinear optical lattices, and study the effects of squeezing a stripe soliton by varying the inter-atomic interaction in the nonlinear lattice. It is observed that the nodes on the soliton arising entirely due to the effect of spin–orbit coupling tend to disappear as we increase the squeezing effect to finally get a stable fundamental soliton. This leads us to conclude that external pressure can reduce the effect of spin–orbit coupling in the SOC BEC and even convert the system to a traditional BEC without spin–orbit coupling. We make use of an information theoretic measure to visualize how does the atomic density distribution in the condensate respond to continual reduction in the spin–orbit coupling effect.

Unveiling multipole physics and frustration of icosahedral magnetic quasicrystals

Multipolar physics and their hidden orders have been widely discussed in the context of heavy fermions and frustrated magnets. However, despite extensive research, there are few examples of purely multipolar systems in the absence of magnetic dipoles. Here, we show the magnetic behavior of an icosahedral quasicrystal is generally described by multipoles, and in a specific case by pure magnetic octupoles, resulting from the interplay of spin-orbit coupling and crystal field splitting. Importantly, we emphasize that non-crystallographic symmetries of quasicrystals result in multipolar degrees of freedom, in contrast to the conventional crystals. We first classify the characteristics of multipoles and derive the effective spin Hamiltonian. We then explore how frustration and quantum fluctuations induce entangled quantum phases. Our study presents the magnetic icosahedral quasicrystal as a platform for investigating the exotic multipolar physics.

Landau‐Level Spectrum and the Effect of Spin–Orbit Coupling in Monolayer Graphene on Transition Metal Dichalcogenides

In graphene on transition metal dichalcogenides, two types of spin–orbit coupling (SOC)—Rashba and spin–valley Zeeman SOCs—can coexist that modify graphene's electronic band differently. Herein, it is shown that the Landau levels (LLs) are also affected by these SOCs distinctively enough to estimate their relative strengths from the Landau fan diagram. A simple theoretical model is used to calculate the LL spectra of graphene for different SOC strengths, revealing that when the total SOC is strong enough (i.e., when it is comparable to the half of the energy gap between the LLs of an intrinsic graphene), the corresponding LLs will split and cross with others depending sensitively on the relative strengths of the SOC terms. To demonstrate how one can use it to estimate the relative SOC strengths, the four key features that are well separated from the complex background are first identified and compared with experiment to show that in the sample investigated, the Rashba SOC is stronger than the spin–valley Zeeman SOC consistent with other spectroscopic measurements. The study therefore provides a simple and practical strategy to analyze the LL spectrum in graphene with SOC before carrying out more in‐depth measurements.

Spin effect in dual-atom catalysts for electrocatalysis.

The development of high-efficiency atomic-level catalysts for energy-conversion and -storage technologies is crucial to address energy shortages. The spin states of diatomic catalysts (DACs) are closely tied to their catalytic activity. Adjusting the spin states of DACs' active centers can directly modify the occupancy of d-orbitals, thereby influencing the bonding strength between metal sites and intermediates as well as the energy transfer during electro reactions. Herein, we discuss various techniques for characterizing the spin states of atomic catalysts and strategies for modulating their active center spin states. Next, we outline recent progress in the study of spin effects in DACs for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), electrocatalytic nitrogen/nitrate reduction reaction (eNRR/NO3RR), and electrocatalytic carbon dioxide reduction reaction (eCO2RR) and provide a detailed explanation of the catalytic mechanisms influenced by the spin regulation of DACs. Finally, we offer insights into the future research directions in this critical field.

Correlation between the spin effect and catalytic activity of two-dimensional metal organic frameworks for the oxygen evolution reaction

We demonstrated that the spin moment of magnetic metals in 2D MOFs is correlated with the stability and catalytic activity of 2D MOFs, which can guide the rational optimization of catalytic activity by tuning the spin states of the metal center.

Spin Effects in tau-lepton Pair Induced by Anomalous Magnetic and Electric Dipole Moments

Spin Effects in tau-lepton Pair Induced by Anomalous Magnetic and Electric Dipole Moments

Spiro-centre substitution effects in the intramolecular spin–spin interactions of spirobiacridine diradicals

Spirodiradicals with the Si and Ge spiro atoms exhibit a S = 1 state. The magnetic interaction in the Si derivative was found to be lower than that in the Ge derivative, implying a negative effect on σ*(Si–Cα)–π* hyperconjugation.

Growth of Bi<sub>2</sub>O<sub>2</sub>Se nanowires and their superconducting quantum interference devices

Bi<sub>2</sub>O<sub>2</sub>Se is a new type of semiconductor material, which has the advantages of high carrier mobility, air stability, strong spin-orbit coupling, etc. It has a variety of synthesis methods and a wide range of applications. In the past few years, many explorations have been made in the synthesis, large-size growth, and applications of Bi<sub>2</sub>O<sub>2</sub>Se. It has been applied to field effect transistors, infrared photodetectors, semiconductor devices, heterojunctions, spin electronics, etc. Since nanowire has a larger surface area-to-volume ratio than nano-film, nanowire may have greater advantages in gate regulation and strong spin-orbit coupling, and these properties can play a crucial role in certain fields. However, most of the studies focused on its two-dimensional films, and there are less researches of its one-dimensional counterpart. In this work, a method of growing Bi<sub>2</sub>O<sub>2</sub>Se one-dimensional nanowires by chemical vapor deposition in a three-temperature-zone tubular furnace is introduced. High-quality suspended Bi<sub>2</sub>O<sub>2</sub>Se nanowires are obtained. In addition, the effects on the Bi<sub>2</sub>O<sub>2</sub>Se nanowire growth of the position of the mica substrates, i.e, different horizontal positions and vertical heights in the quartz boat, are studied, and the optimal conditions for the growth are summarized. The nanowires are characterized by atomic force microscope and energy dispersive spectrometer to show the information about the size and component. Then, superconducting quantum interference device based on the Bi<sub>2</sub>O<sub>2</sub>Se nanowires is constructed, and the superconducting quantum interference in a magnetic field is observed, which provides a way to broaden the application of Bi<sub>2</sub>O<sub>2</sub>Se nanowires.

Mass and tidal parameter extraction from gravitational waves of binary neutron stars mergers using deep learning

Gravitational Waves (GWs) from coalescing binaries carry crucial information about their component sources, like mass, spin and tidal effects. This implies that the analysis of GW signals from binary neutron star mergers can offer unique opportunities to extract information about the tidal properties of NSs, thereby adding constraints to the NS equation of state. In this work, we use Deep Learning (DL) techniques to overcome the computational challenges confronted in conventional methods of matched-filtering and Bayesian analyses for signal-detection and parameter-estimation. We devise a DL approach to classify GW signals from binary black hole and binary neutron star mergers. We further employ DL to analyze simulated GWs from binary neutron star merger events for parameter estimation, in particular, the regression of mass and tidal deformability of the component objects. The results presented in this work demonstrate the promising potential of DL techniques in GW analysis, paving the way for further advancement in this rapidly evolving field. The proposed approach is an efficient alternative to explore the wealth of information contained within GW signals of binary neutron star mergers, which can further help constrain the NS EoS.

Magnetic behaviour of a spin-canted asymmetric lanthanide quinolate trimer.

An asymmetrical dysprosium trimer with a molecular formula of [Dy3(hq)7(hqH)(NO3)2(H2O)] was obtained through a reflux reaction employing as starting material Dy(NO3)3·nH2O and 8-quinolinoline as ligand. Magnetic susceptibility investigations show the system to be an SMM, which was corroborated by sub-Kelvin μSQUID studies. Upon cooling, the magnetic susceptibility also exhibits a decrease in the χMT product, which was confirmed to be due to intramolecular antiferromagnetic interactions. μSQUID measurements, moreover, reveal a marked magnetic behaviour in the angular dependence of the hysteresis loops. The latter is a direct consequence of the non-colinear spin arrangement of the anisotropy axes of each Dy(III) ion in [Dy3(hq)7(hqH)(NO3)2(H2O)] and the interaction between the ions, as also evidenced by CASSCF calculations. Our results evidence the effect of spin canting along with the intramolecular interactions, which can induce non-trivial magnetic behaviour in SMMs.

Numerical Study on the Effect of Spinning for 7.62 APM2 Projectile Impacting on Al 7075-T651 Target

When a projectile launches from a rifled barrel, it undergoes rotation around its longitudinal axis, commonly referred to as spinning, to maintain stability during its flight through the air. Upon reaching the target, the projectile possesses both rotational and translational energies. This study examines the impact of rotational energy on the penetration of 7.62 APM2 projectiles by using Finite Element Analysis(FEA). Al 7075-T651 alloy with a thickness of 20mm is considered as target material. Initially, the model is validated using the experimental results available in the literature. The validated model has been extended to study the effect of the projectile’s spinning by using the Recht-Ipson parameters. Based on the results, it is observed that the rotation of the projectile leads to an enhancement in penetrating energy and a reduction in ballistic limit velocity.

Quantification of the thermodynamic effects of the low-spin - high-spin interaction in molecular crystals of a mononuclear iron(II) spin crossover complex.

A method is proposed to estimate the energetic and entropic effects of spins of neighbouring molecules on the spin transition of a mononuclear spin crossover (SCO) complex in a molecular crystal. Density functional theory (DFT) methods have been used to model the SCO material [FeII(Lnpdtz)2(NCS)2] (Lnpdtz = 2-naphthyl-5-pyridyl-1,2,4-thiadiazole) exhibiting numerous π-π interactions using a 2D arrangement of 15 molecules. The modelling considers only the effects in the crystallographical ac plane with a particularly pronounced stacking but paves the way for future work with 3D arrangements which are computational much more costly. It involves the optimisation and normal mode calculation of the molecules in a rigid matrix of both low-spin (LS) and high-spin (HS) neighbours. This procedure has been used to calculate the previously defined cooperativity parameter Hcoop (S. Rackwitz, W. Klopper, V. Schünemann and J. A. Wolny, Phys. Chem. Chem. Phys., 2013, 15, 15450). For [FeII(Lnpdtz)2(NCS)] we obtain Hcoop = 11 kJ mol-1, a value which is comparable to those found for 3D polynuclear spin crossover materials. A normal mode analysis of the optimised centrally located molecule indicates that the vibrational entropy of the spin transition is somewhat higher (5 J K-1 mol-1) for the LS to HS transition in the LS matrix than in the HS one. The calculations show that the interactions with the neighbours influence the low-frequency modes with wave numbers <65-70 cm-1. These cause the main difference in the vibrational entropy of the spin transition for the vicinity of high- and low-spin molecules. Furthermore, a deformation of the coordination sphere of the central molecule is observed when the spins of the surrounding centres are switched. This deformation is accompanied by a change in the equatorial Fe-N bond lengths.

Patterns of Grain Fragmentation During Plastic Deformation of Metals at Small to Medium Strains (Brief Review)

Due to high carrier mobility and long spin diffusion length graphene is a promising material for spintronics applications. In order to achieve effective spin transport and increase spin injection efficiency, graphene interfaces with highly spin-polarised materials, such as Heusler alloys, are needed. In this work, first-principles calculations of graphene/Co2FeSi electronic structure are done in the frame of density functional theory. It is shown that the high percent of spin polarization in this system is combined with the linear dispersion of the π-states of graphene. The results suggest that the Co2FeSi Heusler alloy is a promising candidate for graphene-based spintronic devices.

Theoretical prediction of C- and O-doped Hittorf’s violet phosphorene as bipolar magnetic semiconductor material

Hittorf’s violet phosphorene is a novel two-dimensional material with stable structure and excellent optoelectronic properties. Studying the doping effect helps to understand its physical essence and is of great significance in further developing nanoelectronic devices. In this paper, the first-principles method based on density functional theory is used to study the electromagnetic properties of the non-metallic element B-, C-, N-, and O-doped single-layer violet phosphene. The results show that there is no magnetism after having doped boron and nitrogen, and the system still behaves as a nonmagnetic semiconductor, while carbon doping and oxygen doping cause spin splitting, and the violet phosphorene transforms from a nonmagnetic semiconductor to a bipolar magnetic semiconductor, and its spin density is mainly distributed in the P atom and gap region, rather than on the impurity. The direction of spin polarization of its carrier can be reversed by adjusting the electric field of O-doped violet phosphorene. When a certain size of forward or reverse electrostatic field is applied, the band dispersion becomes stronger, and the O-doped violet phosphorene transforms into a half-metallic magnet with 100% downward or upward spin polarization at the Fermi level. The field effect spin filter based on O-doped violet phosphorene can reverse the direction of spin-polarized current by changing the direction of the gate voltage. This study shows that O-doped violet phosphorene is expected to be an ideal candidate material for two-dimensional spin field-effect transistors, bipolar magnetic spintronic devices, dual channel field effect spin filters, and field-effect spin valves.

Physical properties of ferromagnetic Mn-doped double perovskites (DPs) Cs2AgInCl/Br6 for spintronics and solar cell devices: DFT calculations.

A computational framework based on density functional theory (DFT) has been effectively employed to investigate the wide-ranging physical characteristics of ferromagnetic manganese (Mn)-substituted double perovskites (DPs) with composition Cs2AgIn1-xMnxCl/Br6 (x = 0.0, 0.25). This research covers a systematic exploration of the mentioned DPs for potential applications in the domains of spintronics and energy conversion devices. The physics concerning ferromagnetic (FM) Cs2AgIn0.75Mn0.25Cl/Br6 DPs was studied computationally using the modified Becke-Johnson (mBJ-LDA) potential and the generalized gradient approximation (PBEsol GGA) method introduced by Perdew, Burke, and Ernzerhof. The structural, electronic, magnetic, and transport behavior of materials were investigated using these computations. Structural parameters for both perovskite materials were computed subsequent to their optimization in FM phase. According to evaluations of the electronic band structure and density of states (DOS), the incorporation of Mn ions into the host lattice causes exchange splitting induced by p-d hybridization, consequently stabilizing the FM state. Probing the sharing of magnetic moment, charge, and spin between the substituent cations and the host anions led to the comprehensive elaboration of this exchange splitting of bands. Important parameters such as exchange constants (N0α, N0β), and direct spin-exchange splitting Δx(d), support the stability of the FM state. Finally, we briefly explored the spin effect on other aspects of electronic transport, the Seebeck coefficient, and the power factor, using the conventional Boltzmann transport theory.

Spin-Vibronic Dynamics in Open-Shell Systems beyond the Spin Hamiltonian Formalism.

Vibronic coupling has a dramatic influence over a large number of molecular processes, ranging from photochemistry to spin relaxation and electronic transport. The simulation of vibronic coupling with multireference wave function methods has been largely applied to organic compounds, and only early efforts are available for open-shell systems such as transition metal and lanthanide complexes. In this work, we derive a numerical strategy to differentiate the molecular electronic Hamiltonian in the context of multireference ab initio methods and inclusive of spin-orbit coupling effects. We then provide a formulation of open quantum system dynamics able to predict the time evolution of the electron density matrix under the influence of a Markovian phonon bath up to fourth-order perturbation theory. We apply our method to Co(II) and Dy(III) molecular complexes exhibiting long spin relaxation times and successfully validate our strategy against the use of an effective spin Hamiltonian. Our study sheds light on the nature of vibronic coupling, the importance of electronic excited states in spin relaxation, and the need for high-level computational chemistry to quantify it.

Spin and orbital Edelstein effect in a bilayer system with Rashba interaction

Spin and orbital Edelstein effect in a bilayer system with Rashba interaction