Metallic Spin Research Articles

Spin and orbital Hall effect in nonmagnetic transition metals: Extrinsic versus intrinsic contributions

Spin and orbital Hall effect in nonmagnetic transition metals: Extrinsic versus intrinsic contributions

TASA formulation for nonlinear radiative flow of Walter-B nanoliquid invoking microorganism and entropy generation

Recent scientists and engineers have keen interest for nanomaterial flow across the globe. It is because of the fact that nanomaterials possess innovative characteristics that have gained considerable attention for their involvement in medicine, automobiles, metal spinning, heat transfer and storage devices, power generation, renewable energy and many others. Heat transfer rate has key role regarding finishing and quality of end product. With such consideration the present communication analyzes magnetohydrodynamic bioconvective flow of Walter-B nanoliquid. Flow is generated by stretching surface. Gyrotactic microorganisms in presence of first order reaction is discussed. Energy expression comprises Brownian movement, magnetohydrodynamics, thermophoresis, thermal radiation and dissipation characteristics. Innovative features (random movement and thermophoresis) of Buongiorno's model are deliberated. Entropy minimization rate is under consideration. Soret effect in first order reactive flow is considered. Bejan number is calculated. Dimensionless ordinary expressions are developed through suitable transformations. Optimal homotopy analysis method (OHAM) is invoked for convergence purposes. Total and individual residual errors have been computed through OHAM which guarantees the solutions convergence. Graphical analysis for entropy rate, microorganism field, liquid motion, temperature, Bejan number and concentration is arranged. In addition, the analysis for skin friction, motile density number and Nusselt and Sherwood numbers is organized. Here velocity and Bejan number decreased against larger magnetic field whereas opposite scenerio witnessed regarding thermal field and entropy rate. Decrease in liquid motion occurs through viscoelastic variable while an increasing effect seen for thermal transport rate. Higher Prandtl number lead to intensify the thermal transport rate. Nusselt number and entropy rate for radiation have similar response qualitatively when compared with concentration through higher Soret number.

Manipulation of d-Orbital Electron Configurations in Nonplanar Fe-Based Electrocatalysts for Efficient Oxygen Reduction.

Manipulation of the spin state holds great promise to improve the electrochemical activity of transition metal-based catalysts. However, the underlying relationship between the nonplanar metal coordination environment and spin states remains to be explored. Herein, we report the precise regulation of nonplanar Fe atomic d-orbital energy level into an irregular tetrahedral crystal field configuration by introducing P atoms. With the increase of P coordination number, the spin magnetic moment decreases linearly from 3.8 μB to 0.2 μB, and the high spin content decreases linearly from 31% to 5%. Significantly, a volcanic curve between the spin states of Fe-based catalysts (Fe-NxPy) and oxygen reduction reaction (ORR) activity has been unequivocally established based on the thermodynamic results. Thus, the Fe-N3P1 catalyst with a 19% medium spin state experimentally exhibits the optimal reaction activity with a high half-wave potential of 0.92 V. These findings indicate that regulating electron spin moments through coordination engineering is a promising catalyst design strategy, providing important insights into spin catalysis.

Spin-Polarized Antiferromagnetic Metals

Spin-polarized antiferromagnets have recently gained significant interest because they combine the advantages of both ferromagnets (spin polarization) and antiferromagnets (absence of net magnetization) for spintronics applications. In particular, spin-polarized antiferromagnetic metals can be useful as active spintronics materials because of their high electrical and thermal conductivities and their ability to host strong interactions between charge transport and magnetic spin textures. We review spin and charge transport phenomena in spin-polarized antiferromagnetic metals in which the interplay of metallic conductivity and spin-split bands offers novel practical applications and new fundamental insights into antiferromagnetism. We focus on three types of antiferromagnets: canted antiferromagnets, noncollinear antiferromagnets, and collinear altermagnets. We also discuss how the investigation of spin-polarized antiferromagnetic metals can open doors to future research directions.

Designing delafossite CuAl1-xTMxO2 solid solutions: the role of 3d transition metal spin states in photo(electro)catalytic performance

This study delves into the effects of 3d transition metal (TM) spin states on the structural and electronic properties of CuAl1-xTMxO2 solid solutions, focusing on their implications for photo(electro)catalytic performance. The research reveals that the Jahn–Teller distortion, associated with TM3+, is a critical factor in determining the lattice parameters and photo(electro)catalytic performances. Solid solutions without Jahn–Teller distortion adhere to Vegard's law, whereas those with strong distortion exhibit deviations, indicating the influence of TMO6 octahedral distortion on solubility and lattice parameters. The electronic structure of solid solutions with weak Jahn–Teller distortion is governed by the O–Cu–O and TMO6 crystal fields, which leads to a narrowed bandgap and reduced conduction band minimum (CBM), impacting the hydrogen evolution potential. In particular, the CuAl0.5Cr0.5O2 shows a significant enhancement in photocurrent density and hydrogen production rate due to its balanced light absorption and effective charge carrier separation. In contrast, the weak Jahn–Teller distortion in CuAl1-xFexO2 results in localized electronic states at CBM, leading to diminished carrier mobility. Solid solutions with strong Jahn–Teller distortion, such as CuAl1-xTMxO2 (TM = Mn and Ni), display a range of electronic properties from semiconductor to semimetallic, with the semimetallic CuAl0.9Mn0.1O2 capable of infrared light absorption and efficient photocatalytic hydrogen and oxygen production.

Environmentally persistent free radicals and other paramagnetic species in wildland-urban interface fire ashes

Wildland-urban interface (WUI) fires consume fuels, such as vegetation and structural materials, leaving behind ash composed primarily of pyrogenic carbon and metal oxides. However, there is currently limited understanding of the role of WUI fire ash from different sources as a source of paramagnetic species such as environmentally persistent free radicals (EPFRs) and transition metals in the environment. Electron paramagnetic resonance (EPR) was used to detect and quantify paramagnetic species, including organic persistent free radicals and transition metal spins, in fifty-three fire ash and soil samples collected following the North Complex Fire and the Sonoma-Lake-Napa Unit (LNU) Lightning Complex Fire, California, 2020. High concentrations of organic EPFRs (e.g., 1.4 × 1014 to 1.9 × 1017 spins g−1) were detected in the studied WUI fire ash along with other paramagnetic species such as iron and manganese oxides, as well as Fe3+ and Mn2+ ions. The mean concentrations of EPFRs in various ash types decreased following the order: vegetation ash (1.1 × 1017 ± 1.1 × 1017 spins g−1) > structural ash (1.6 × 1016 ± 3.7 × 1016 spins g−1) > vehicle ash (6.4 × 1015 ± 8.6 × 1015 spins g−1) > soil (3.2 × 1015 ± 3.7 × 1015 spins g−1). The mean concentrations of EPFRs decreased with increased combustion completeness indicated by ash color; black (1.1 × 1017 ± 1.1 × 1017 spins g−1) > white (2.5 × 1016 ± 4.4 × 1016 spins g−1) > gray (1.8 × 1016 ± 2.4 × 1016 spins g−1). In contrast, the relative amounts of reduced Mn2+ ions increased with increased combustion completeness. Thus, WUI fire ash is an important global source of EPFRs and reduced metal species (e.g., Mn2+). Further research is needed to underpin the formation, transformation, and environmental and human health impacts of these paramagnetic species in light of the projected increased frequency, size, and severity of WUI fires.

Exact Numerical Solution of the Fully Connected Classical and Quantum Heisenberg Spin Glass.

We present the mean field solution of the quantum and classical Heisenberg spin glasses, using the combination of a high precision numerical solution of the Parisi full replica symmetry breaking equations and a continuous time quantum MonteCarlo algorithm. We characterize the spin glass order and its low-energy excitations down to zero temperature. The Heisenberg spin glass has a rougher energy landscape than its Ising analog, and exhibits a very slow temperature evolution of its dynamical properties. We extend our analysis to the doped, metallic Heisenberg spin glass, which displays unexpectedly slow spin dynamics, reflecting the proximity to the melting quantum critical point and its associated Sachdev-Ye-Kitaev Planckian dynamics.

An exploration of diffusion-thermo and radiation absorption impacts on non-Newtonian MHD flow towards two distinct geometries with biot number

Temperature and liquid flow monitoring are required in many industrial applications in order to maximize machine performance. When exploring polymers, fabricating synthetic films and transparent materials, and manufacturing metal-based equipment, frictional forces and thermal flow rates need to be controlled. The significance of the study of prominent characteristics of Diffusion-Thermo, Quadratic thermal radiation and radiation absorption over a permeable stretching geometry are discussed. Similarity transformations reduced the boundary layer partial differential to an ODE. The acquired system of ODEs is solved in numerical-manner using MATLAB bvp4c. The distributions f '(η), θ(η) and φ(η) are described graphical aspect, with specified governed parameters. As Diffusion thermo parameter raises, temperature field enhances. As radiation absorption raises, the temperature and velocity enhance and concentration decreases. A rise in radiation absorption parameter causes a raise in the buoyancy, which in turn raises the flow rate, and that this is reflected in the velocity profiles. The radiation absorption parameter raises temperatures nearer porous boundary layer and lowers concentration. Rising temperature ratio parameter θw values were accompanied by rising temperatures. Temperature is enhancing when improving of Biot parameter. The skin-friction is heightened with raising ‘n’ values. Nusselt number is declined, raising values of Df. The Sherwood number is enhanced with raising values of ‘Sc’. An incorporation of Diffusion thermo, Quadratic thermal radiation and radiation absorption effects in a nano-Carreau flow across Wedge and Cone is the novelty. The flow of a boundary-layer across a wedge gets made growingly significant, not long ago, owing to its many practical applications, including those in medical, bioengineering, crude oil extraction, nuclear power plants, a polymer extrusion process, production of plastic sheet, metal spinning, friction drag of a ship, and electronic gadgets, etc. This study will be extended by incorporating micro-polar, tangent hyperbolic, Sutterby, with distinct non-Newtonian fluids.

Quantification of the Donor-Acceptor Character of Ligands by the Effective Fragment Orbitals.

Metal-ligand interactions are at the heart of transition metal complexes. The Dewar-Chat-Duncanson model is often invoked, whereby the metal-ligand bonding is decomposed into the simultaneous ligand→metal electron donation and the metal→ligand back-donation. The separate quantification of both effects is not a trivial task, neither from experimental nor computational exercises. In this work we present the effective fragment orbitals (EFOs) and their occupations as a general procedure beyond the Kohn-Sham density functional theory (KS-DFT) framework for the identification and quantification of donor-acceptor interactions, using solely the wavefunction of the complex. Using a common Fe(II) octahedral complex framework, we quantify the σ-donor, π-donor, and π-acceptor character for a large and chemically diverse set of ligands, by introducing the respective descriptors σd, πd, and πa. We also explore the effect of the metal size, coordination number, and spin state on the donor/acceptor features. The spin-state is shown to be the most critical effect, inducing a systematic decrease of the sigma donation and π-backdonation going from low spin to high spin. Finally, we illustrate the ability of the EFOs to rationalize the Tolman electronic parameter and the trans influence in planar square complexes in terms of these new descriptors.

Micromagnetic modeling of double spin-torque magnetic tunnel junction devices

Emerging nonvolatile magnetoresistive random access memory exhibits high endurance and long data retention compared to flash memory. Additionally, devices with double spin torque magnetic tunnel junctions (dsMTJ) featuring two magnetic reference layers demonstrate enhanced torques, fast switching, and reduced switching currents. To accurately model these devices, we adopt a coupled spin and charge transport approach allowing to describe spin-transfer torques in metallic spin valves and magnetic tunnel junctions on equal footing. Our findings indicate the critical influence of metallic non-magnetic spacers (NMS) properties separating the free layer from the second reference layer on the switching speed improvement in dsMTJ devices.

Radiative bioconvective flow with non-uniform heat source and Soret and Dufour impacts

Background and objectiveThe stretched flow with heat transfer has pivotal role in geothermal energy system, oil extraction, continuous casting, metal spinning and electronic cooling. Owing to this fact, the current analysis focuses on non-linear thermal radiation effect in bio-convective stagnation point flow by a stretchable wedge. Darcy relation is used to discuss the porous space. Convective conditions are deliberated. Non-uniform heat source is addressed. Soret and Dufour outcomes are analyzed. Dissipation and magnetohydrodynamics are discussed. Presence of gyrotactic microorganisms along with chemical reaction is considered. MethodologyRelated non-linear partial differential equations (PDEs) are reduced into dimensionless ordinary differential equations (ODEs) through adequate transformations. Optimal homotopy analysis method (OHAM) is adopted for the computations of related nonlinear differential systems. ResultsFlow, microorganism field, concentration and temperature distribution are graphically explored. Numerical analysis for coefficient of skin friction, microorganism density number and Sherwood and Nusselt numbers against emerging parameters are discussed. It is noted that velocity and skin friction coefficient have similar scenario for modified Hartman number. Thermal transport rate and temperature have reverse trends for non-uniform heat source variable. An augmentation in thermal distribution is seen through thermal Biot number. Larger Dufour number has increasing trend for temperature. An increasing trend for solutal Biot number for concentration is noticed. Larger Soret number leads to concentration enhancement. Microorganism field and motile density number against Peclet number have opposite response. There is reduction for bio-convective Lewis number in motile density number.

Numerical investigation of electroosmotic driven transport of MHD Casson fluid over an exponential stretching sheet using quartic B-spline method

The stretching surface flow phenomenon plays novel significance in the differential industrial sectors like manufacturing processes, food processing, polymers, petroleum engineering, glass fiber production, metal spinning, and many others. This research focuses on investigating the flow of electroosmotic-driven transport of magnetic Casson fluid over an exponential stretching sheet. The study employs mathematical modeling based on partial differential equations which are further truncated into ordinary system under the implementation of dimensionless variables. The quartic B-spline method is applied for obtaining solutions. Key findings indicate that electroosmotic and Helmholtz–Smoluchowski effects enhance fluid velocity, while magnetic forces reduce velocity. Additionally, an increase in the Hartmann parameter leads to a decrease in the skin friction coefficient.

Computer Aided Engineering in the application of rotational forming of axially asymmetric geometries

The research presents the results of an innovative metal forming technology: ‘axially asymmetric metal spinning’. Special attention was paid to the influence of two forming conditions: Constant Contact (CC) and Tangential Contact (TC). The influence of Constant Contact and Tangential Contact were examined and compared. The term Constant Contact was used to describe a forming zone fixed at a certain height. This attribute was defined as naturally occurring in axially symmetrical metal spinning. The term Tangential Contact was used as the opposite to Constant Contact. Tangential Contact was used to describe the phenomena of movement of the forming zone. This attribute was defined as naturally occurring in axially asymmetric metal spinning. For the purpose of comparison, an asymmetric mandrel was manufactured, for which two trajectories were engineered. The trajectories were designed with the CC and TC conditions. The Finite Element Method was used to conduct metal forming simulation in simufact.forming software. Experimental trials were performed on the spinning machine MWS—200. Aluminium Alloy 1050 A was used in the FEM and experimental tests. The geometry measurement was performed using an ATOS 3D scanner and GOM Inspect software. The measurement of residual stresses was performed on a Proto iXRD® diffractometer. After determining the specific requirements of the innovative axially asymmetric spinning technology, a special computer program, called RoMeFo, was created. RoMeFo’s purpose was to engineer the trajectory with the TC condition for the mandrel’s full height. Depending on the method used, details with the following heights were manufactured in the experimental trials: CC—22 mm, TC—30 mm and RoMeFo—60 mm.

Numerical Analysis on Stagnation Point Flow of Micropolar Nanofluid with Thermal Radiations over an Exponentially Stretching Surface

Several industrial developments such as polymer extrusion in metal spinning and continuous metal casting include energy transmission and flow over a stretchy surface. In this paper, the stagnation point flow of micropolar nanofluid over a slanted surface is presenting also considering the influence of thermal radiations. Buongiorno’s nanoliquid model is deployed to recover the thermophoretic effects. By using similarity transformations, the governing boundary layer equations are transformed into ordinary differential equations. The Keller-box approach is used to solve transformed equations numerically. The numerical outcomes are presented in tabular and graphical form. A comparison of the outcomes attained with previously published results is done after providing the entire formulation of the Keller-Box approach for the flow problem under consideration. It has been found that the reduced sherwood number grows for increasing values of radiation parameter while, reduced Nusselt number and skin friction coefficient decreases. Furthermore, the skin-friction coefficient increases as the inclination factor increases, but Nusselt and Sherwood's numbers decline.

Effect of Intermediate Path on Post-Wrinkle Initiation of the Multi-Pass Metal Spinning Process: Analysis in the Rotating Reference Frame

The metal spinning process has been observed in recent major investigations carried out using finite element analysis. One interesting idea has proposed simulating a rotating disc for the simulation of the metal spinning process to reduce computational time. The development of this concept is presented in this paper, including the formal mathematical transformation from the inertial frame to the rotating reference frame, specific FEM configurations with mesh sizes based on a minimized aspect ratio, a mesh convergence study, and the application of a feed rate scale. Furthermore, in the context of the rotating reference frame, the flange geometry after wrinkle initiation is investigated, including the number of peaks and their amplitudes. Using this new approach, it was found that the number of peaks gradually increases from two to eight peaks while their amplitude decreases. In the case of severe wrinkles, the number of peaks stays at four while the amplitude increases dramatically. The intermediate path proves capable of increasing the number of peaks while maintaining a low amplitude. These results will make it possible to design new paths, facilitating the production of defect-free spun parts.

Correlating active sites and oxidative species in single-atom catalyzed Fenton-like reactions.

Single-atom catalysts (SACs) have gained widespread popularity in heterogeneous catalysis-based advanced oxidation processes (AOPs), owing to their optimal metal atom utilization efficiency and excellent recyclability by triggering reactive oxidative species (ROS) for target pollutant oxidation in water. Systematic summaries regarding the correlation between the active sites, catalytic activity, and reactive species of SACs have rarely been reported. This review provides an overview of the catalytic performance of carbon- and metal oxide-supported SACs in Fenton-like reactions, as well as the different oxidation pathways induced by the metal and non-metal active sites, including radical-based pathways (e.g., ·OH and SO4˙-) and nonradical-based pathways (e.g. 1O2, high-valent metal-oxo species, and direct electron transfer). Thereafter, we discuss the effects of metal types, coordination environments, and spin states on the overall catalytic performance and the generated ROS in Fenton-like reactions. Additionally, we provide a perspective on the future challenges and prospects for SACs in water purification.

Study on Nanofluid Boundary Layer Flow Over A Stretching Surface by Spectral Collocation Method

The method of Spectral collocation is used to analyze the flowing Nano fluid layer in contact with a stretching surface for comprehensive information and thus to have its utility in industrial activities like the production of glass fibers, petroleum refining, hot rolling of metals, metal spinning etc. The spectral collocation model incorporates thermophoresis and Brownian motion phenomena to describe the fluid flow, fluid concentration and temperature profiles. A similarity solution has been presented for the governing equations of fluid momentum, concentration and temperature. The computational results are the function of Prandtl number (Pr), Lewis number (Le), thermophoresis and Brownian motion phenomena. The engineering quantities like thermophoresis parameter (Nt), Brownian motion parameter (Nb), buoyancy-ratio parameter (Nr) and reduced Nusselt number (Nu) and reduced Sherwood number (Sh) have tabulated corresponding to Prandtl number (Pr) and Lewis number (Le). The results of the current study thrown light on fluid velocity and heat transfer rates in the boundary layer. The numerous industrial products and manufacturing processes of superior quality can be exercised with the current studies.

Evidence for intrinsic magnetic scatterers in the topological semimetal (Bi2)5(Bi2Se3)7

We report the synthesis and characterization of high-quality thin films of the topological semimetal (Bi2)5(Bi2Se3)7. Cryogenic magneto-transport experiments reveal strong metallic character and spin–orbit coupling in the films. By studying the temperature dependence of the electrical resistance of the topological semimetal, we observe a pronounced Kondo effect, which points toward the presence of magnetic scatterers. With the aid of density functional theory calculations, we identify Bi vacancies as intrinsic magnetic scatterers in this topological semimetal.

Heat and mass transfer in Maxwell fluid with nanoparticles past a stretching sheet in the existence of thermal radiation and chemical reaction

ABSTRACT The objective of this work is to examine the distinctive features of heat and mass transfer in a 2-dimensional Maxwell fluid that is incompressible and contains electrically conducting nanoparticles. They are illustrated by using a stretched sheet with convective boundary conditions and a heat source/sink in the presence of thermal radiation and chemical interaction. Studies of hydromagnetic flow and heat transfer across a stretched sheet have lately attracted a great deal of attention as a result of its numerous industrial applications and a huge impact on a broad variety of manufacturing processes. Power plants, heat exchangers, MHD generators, aerodynamics, plastic sheet extrusion, condensation processes, and metal spinning are examples of these processes. The partial differential equations (PDEs) that govern the flow and the boundary conditions that correspond with them may be non-dimensionalized by using the appropriate similarity variables. The resulting transformed ordinary differential equations (ODEs) are solved using the Runge-Kutta-Fehlberg scheme of the fourth and fifth order. By assuming a value for the boundary condition, the shooting approach transforms the boundary value problem (BVP) into an initial value problem (IVP), which is subsequently solved using the RKF45 algorithm. Graphical representations of how such embedded thermo-physical parameters significantly impact the velocity, temperature, and concentration are assessed and shown. A comparison case study is made with previously published literature, and a great correlation between the results exists. The primary results of the research are that raising estimates of the chemical reaction parameter minimises the concentration distribution while increasing the thermal radiation parameter raises the temperature. As the quantity of thermophoresis rises, the thickness of the boundary layer increases, causing the surface temperature to rise, resulting in a temperature rise.

Exploration of heat and mass transfer on 3-D radiative MHD Casson fluid flow over a stretching permeable sheet with chemical reaction

The goal of this study is to determine the effect of chemical reaction, radiation, and Prandtl number on 3-D MHD Heat transfer Casson fluid flow through a linearly porous stretched surface. When studying the effects of thermal radiation, the Roseland approximation is utilized since it factors the radiation impact into the energy equation. Due to its many commercial uses and significant influence on a wide range of production processes, heat transfer past a stretched sheet has garnered interest recently. They include power plants, heat exchangers, MHD generators, aerodynamics, plastic sheet extrusion, condensation, and metal spinning. Using similarity variables, the governing equations & allied boundary conditions are simplified to a dimensionless form, and then the problem is solved using the Runge-Kutta-Fehlberg strategy. The reliability and precision of this Runge-Kutta-Fehlberg strategy is shown graphically for a range of relevant parameters and conditions. A comparison of our numerical findings with data that had been formerly published reveals that both sets of data are quite compatible with one another. The results of the current research contribute to the regulation of heat transfer rates and fluid velocities in various manufacturing processes and industrial applications, hence facilitating the production of required quality in the final product.