Spin Flow Research Articles

HVAC-solar energy performance exploiting Sutterby (AA7075–Ag–Cu/C6H9NaO7) ternary magnetic nanofluid through spinning flow with joule heating

HVAC-solar energy performance exploiting Sutterby (AA7075–Ag–Cu/C₆H₉NaO₇) ternary magnetic nanofluid through spinning flow with joule heating

Spin-to-charge conversion via dual-mode ferromagnetic resonance in Ta/NiFe/FeMn/CoFeB multilayer

The precise engineering of microwave absorption frequencies is of paramount importance in the advancement of spintronic-based RF devices. In the pursuit of this objective, magnetic thin films demonstrate unrivaled efficacy in enabling external modulation of their microwave responses in a reconfigurable manner. Here, we demonstrate dual-frequency ferromagnetic resonance modes and corresponding spin-to-charge conversion efficiency in thin film structures comprising Ta/NiFe/FeMn/CoFeB multilayer. A systematic thickness variation of the NiFe layer (i.e., 4–20 nm) has been undertaken to elucidate the impact on both static and dynamic properties across the multilayer structure. The presence of two distinct magnetic layers manifests in the emergence of two-step magnetic hysteresis loops, which are incorporated with unique resonant modes. The separation between the resonant fields shows tunable properties with excitation frequencies, thereby offering a wide range of reconfigurable operating parameters. The effective damping parameter has shown a decrement with increasing thickness of the NiFe layers. The effective spin mixing conductance for the NiFe layer was found to be 7.4 ± 0.6 nm−2. The spin-to-charge conversion within these structures has been demonstrated through measurements of the inverse spin Hall effect. Systematic thickness variation revealed that the prominent voltage drop was observed in the NiFe layer compared to the CoFeB layer. Considering the opposite spin Hall angles of Ta and FeMn layer, the direction of the spin flow and spin-to-charge conversion efficiency are summarized.

Dual mode spin to charge conversion using inverse spin Hall effect in NiFe/FeMn/NiFe multilayer thin films

Microwave devices with more than one operating frequency and their ease of tunability are of great importance for high-frequency information processing. Magnetic thin films offer an unparalleled advantage of engineering different microwave bands that can be precisely tailored and reconfigured externally. Here, novel trilayer structures consisting of NiFe/FeMn/NiFe with varying antiferromagnetic FeMn layer thickness have been investigated by exploring their ferromagnetic resonance (FMR) properties and inverse spin Hall effect (ISHE) responses. Two-step magnetic hysteresis loops are observed for higher FeMn thickness (t ⩾ 12 nm), where the bottom NiFe layer shows a comparatively more significant shift due to the presence of strong interfacial exchange coupling. FMR study reveals two resonant modes associated with the two ferromagnetic layers, which are distinguishable for higher thicknesses of FeMn or at high excitation frequencies. The choice of FeMn thickness determines the operating frequencies, which can be finely tailored by optimizing the FeMn thickness. Gilbert damping parameter is found to be in the range of 0.009–0.012 where the presence of exchange bias adds to the the scattering mechanisms. Prominent ISHE responses are obtained from the bottom NiFe layer as compared to the top NiFe layer. Variation of FeMn thickness also shows a strong influence on the spin pumping ( Vsp ), and perpendicular anisotropic magnetoresistance ( VAMR⊥ ) components. The results are correlated with the efficiency of spin flow and spin-to-charge conversion of the FeMn layer. Our systems can be used as an emerging alternative for microwave detectors and microwave energy harvesters.

Harmonic flow of Spin(7)-structures

Harmonic flow of Spin(7)-structures

Transverse spin and energy flow in Kerker scattering

Transverse spin and energy flow in Kerker scattering

Tunable long-range spin transport in a van der Waals Fe3GeTe2/WSe2/Fe3GeTe2 spin valve.

The seamless integration of two-dimensional (2D) ferromagnetic materials with similar or dissimilar materials can widen the scope of low-power spintronics. In this regard, a vertical van der Waals (vdW) heterostructure of 2D ferromagnets with semiconducting transition metal dichalcogenides (TMDCs) forms magnetic junctions with exceptional stability and electrical control. Interestingly, 2D metallic Fe3GeTe2 (FGT) reveals above room temperature Curie temperatures and has large magneto anisotropy due to spin-orbit coupling. In addition, it also possesses topological states and a large Berry curvature. Herein, we designed the FGT/WSe2/FGT vdW heterostructure with a uniform and sharp interface so that FGT could maintain its inherent electronic properties. Also, the uniform thickness of the barrier provides a smooth flow of spins through the junctions as tunneling exponentially decays with an increasing barrier thickness. However, strong energy-dependent spin polarization is crucial for achieving optimum spin valve properties, such as large tunneling magnetoresistance (TMR) along with the manipulation of the magnitude and sign reversal. We have observed a shifting of high-energy localized minority spin states toward low-energy regions, which causes spin polarization fluctuation between -42.5% and 41% over a wide range of bias voltage. This leads to a negative TMR% of ∼-100% at 0.1 V Å-1 and also a large positive TMR% at 0.2 V Å-1 and -0.4 V Å-1. Besides, the system exhibits a highly tunable large anomalous Hall conductivity (AHC) of 626 S cm-1. Interestingly, such unprecedented electronic behaviour with large and switchable spin polarization, anomalous Hall conductivity and TMR can be incorporated into MTJ devices, which provide electrical control and long-range spin transport. Additionally, the system emerges as a standout candidate in low-power spintronic devices (e.g., MRAM and magnetic sensors) owing to its distinctive energy-dependent electronic structure with a wide range of external bias.

Simulation analysis of enhanced fluidization leaching process and geothermal synergy in deep ground metal mines

Based on the mining of deep metal mineral resources and the current in-situ leaching mining process of uranium ore, combined with the technological characteristics of ?fluidized mining of metal ore? and ?deep geothermal development?, an innovative concept of strengthening the fluidized leaching process of deep metal ore - geothermal co mining is proposed, A numerical simulation method was used to analyze the turbulent flow and heat transfer characteristics of a new type of heat transfer enhancement element - a swirl plate as a support between tubes. The renormalization two equation turbulence model was used for numerical simulation, and the SIMPLEC algorithm was used for pressure and velocity coupling, and the enhanced wall treatment method was used for wall treatment. The periodic changes in the cross-sectional flow field and turbulence intensity of the unit flow channel were analyzed, as well as the synergistic relationship between the flow field and temperature field on the cross-section. The corresponding variation trends of the average Nusselt number and the average synergy angle of the cross-section were compared. The experimental results show that the 270-4.25 cyclone sheet can more fully utilize the enhanced heat transfer of the spin flow, and the overall average Nusselt number is higher than 180-2.0, which is consistent with the experimental results. That is, ?m is low where high Nub and ?m is high where low Nub is low, indicating that the changing trend of the two is fully consistent with the field synergy principle. This paper systematically analyzes the basic theoretical bottleneck, key technical problems and future development trend in the process of geothermal joint mining of deep metal mine, and aims to provide reference for the strengthening of geothermal joint mining and geothermal joint mining of deep metal ore.

Macromolecular structure development of dry-spinning UHMWPE fibers through the industrial high-ratio hot-drawing process

Ultra-high molecular weight polyethylene (UHMWPE) and its decalin suspension were subjected to several industrial processes including swelling, dissolving, spinning, drying, and multi-stage high-ratio hot drawing to fabricate UHMWPE fibers (UPE fibers). The morphologies and architectures of the UPE fibers at different drawing stages were characterized by polarizing optical microscope (POM), scanning electron microscope (SEM) and atomic force microscopy (AFM). The aggregation structure evolution of UHMWPE macromolecules during the high-ratio hot-drawing process was studied by differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and other testing methods. The experimental results demonstrated that the UHMWPE/decalin spinning suspension was extruded from the spinneret hole to form a fine spinning flow, followed by the formation of the transitional-state fibers at different processing stages, and finally the ready-made fibers. The total drafting ratio of the UPE fibers after fabrication reached more than 600 times. The diameter of the single UPE filament was reduced to 5.66 μm with elevated drawing ratios. The crystal structure of the prepared UPE fibers was progressively improved, and the folding-chain crystals of fibers gradually transformed into extended-chain crystals. The mechanical properties of the UPE fibers were significantly improved. The fracture strength of the as-spun UPE fibers reaches 48.1 cN/dtex, which endows the fibers with specific characteristics such as ultra-fine denier and ultra-high strength.

Charge and spin thermoelectric transport in benzene-based molecular nano-junctions: a quantum many-body study.

Within the Coulomb blockade regime, our study delves into the charge, spin, and thermoelectric transport characteristics of a benzene-based molecular nano-junction using the Pauli master equation and linear response theory. The charge- and spin-transport studies show strong negative differential conductance features in the current-voltage (I-V) characteristics for the ortho and meta connections of electrodes on either side. Contrarily, the para-connection displays Coulomb staircase behavior. By exploring spin current behavior in the presence of spin-polarized electrodes or an external Zeeman field, we establish a methodology that facilitates precise control over the specific spin flow. Various charge and spin thermoelectric transport coefficients have been studied with varying chemical potentials. We focus on spin-polarized conductance, the Seebeck coefficient, and the figure of merit. By adjusting electrode polarization or employing an external magnetic field, we achieve an impressive peak value for the spin thermoelectric figure of merit, approximately 4.10. This outcome underscores the strategic value of harnessing both spin-polarized electrodes and external magnetic fields within the domain of spin caloritronics.

Light-induced ultrafast spin transport in multilayer metallic films originates from sp - d spin exchange coupling

Ultrafast interaction between the femtosecond laser pulse and the magnetic metal provides an efficient way to manipulate the magnetic states of matter. Numerous experimental advancements have been made on multilayer metallic films in the last two decades. However, the underlying physics remains unclear. Here, relying on an efficient ab initio spin dynamics simulation algorithm, we revealed the physics that can unify the progress in different experiments. We found that light-induced ultrafast spin transport in multilayer metallic films originates from the sp - d spin-exchange interaction, which can induce an ultrafast, large, and pure spin current from ferromagnetic metal to nonmagnetic metal without charge carrier transport. The resulting trends of spin demagnetization and spin flow are consistent with most experiments. It can explain a variety of ultrafast light-spin manipulation experiments with different systems and different pump-probe technologies, covering a wide range of work in this field.

Coherent spin transport in an Fe-S protein

Spin transport in a molecule was recently examined to discuss the chiral-induced spin selectivity (CISS) effect. This effect has been particularly reported in metalloproteins because the presence of transition metals improves spin polarization in a helical peptide structure. Among metalloproteins, iron-sulfur proteins have ubiquitous redox properties in photosynthesis and respiration. Iron can enhance spin polarization. In this study, the coherent spin transport in an Fe-S protein was investigated using first-principles calculations based on the Landauer formula. Proteins containing the [4Fe-4S] cluster were used for the calculations. The results of the spin transmission pathway revealed spin flow via Fe-S clusters.

The radiative composite (NiCr + TC4/H2O) mixture nanofluid flow over a non-linear spinning stretching sheet with the impact of variable Lorenz force and slip condition

Significance The hybrid nanofluid flow is an exciting area of research nowadays for various applications like solar thermal systems, aircrafts, heat exchangers, cooling systems and medical applications. Aim The present research explores the numerical analysis of the three-dimensional spinning flow of a hybrid nano-liquid (NiCr + TC4) over a nonlinear stretching sheet with boundary slip. Methodology The flow equations are governed as partial differential equations (PDEs) and then converted into ordinary differential equations (ODEs) via scaling transformations. In order to compute a solution to the nonlinear ODEs, the Runge-Kutta Fehlberg scheme is used along with MATLAB. Results The findings demonstrate that the temperature field rises with an increase in nanoparticle volume fraction () and falls with an increase in Prandtl number Pr. The wall shear stress in the hybrid nanofluid flow is 1.2% more than viscous fluid flow for different index parameter (n) values. In addition, thermal radiation and magnetic effects widen the study and provide useful insights into the behavior of nano-liquid under various aspects. Novelty This article explores the computational analysis of the 3D rotating flow of (NiCr + TC4)/H2O hybrid nano-liquid across a nonlinear stretching sheet under boundary slip conditions. This flow also takes into account the effect of the variable magnetic field and heat radiation.

Manipulation of local angular momentum in the tightly focused optical field via the variation of polarization in radial direction

The redistribution of angular momentum density can be achieved by tightly focusing the special vector optical fields, which can induce the orbital motion of the microscopic particles. Here, we investigate the focusing properties of radial-variant hybridly polarized vector optical fields with the polarization state varying along the different circular trajectories of the Poincaré sphere. It is found that the redistribution of local angular momentum is induced by the assembling of asymmetric spin flow derived from the orthogonal circularly polarized components of the vector optical field. On this basis, we present an effective method for flexibly manipulating the angular momentum density distribution by customizing the variations of polarization corresponding to different circular trajectories on the Poincaré sphere. These works may promote the applications of vector optical field in optical microfabrication and micro-manipulation.

Long-lived spin waves in a metallic antiferromagnet

Collective spin excitations in magnetically ordered crystals, called magnons or spin waves, can serve as carriers in novel spintronic devices with ultralow energy consumption. The generation of well-detectable spin flows requires long lifetimes of high-frequency magnons. In general, the lifetime of spin waves in a metal is substantially reduced due to a strong coupling of magnons to the Stoner continuum. This makes metals unattractive for use as components for magnonic devices. Here, we present the metallic antiferromagnet CeCo2P2, which exhibits long-living magnons even in the terahertz (THz) regime. For CeCo2P2, our first-principle calculations predict a suppression of low-energy spin-flip Stoner excitations, which is verified by resonant inelastic X-ray scattering measurements. By comparison to the isostructural compound LaCo2P2, we show how small structural changes can dramatically alter the electronic structure around the Fermi level leading to the classical picture of the strongly damped magnons intrinsic to metallic systems. Our results not only demonstrate that long-lived magnons in the THz regime can exist in bulk metallic systems, but they also open a path for an efficient search for metallic magnetic systems in which undamped THz magnons can be excited.

Preparation and characterization of polyvinylidene fluoride/graphene composite membranes via the electrostatic spinning method

The polyvinylidene fluoride/graphene composite membranes were prepared by electrostatic spinning under different conditions. Statistical analysis was conducted on the film-forming properties and liquid absorption rate. Scanning electron imaging technology observed the typical morphologies of the prepared membranes. The influences of process conditions, such as the graphene content, the applied voltage, the needle-collector distance, and the spinning flow rate on the typical morphology of the composites, were compared. It was found that the applied and the needle-collector distance significantly affected the thin film’s film-forming properties. In contrast, the flow rate had a smaller effect on the film properties and morphology. Comprehensive comparison results suggested that the morphology and uniformity of the fibers in the prepared composite material were relatively better at the needle-collector distance of 13 cm with a graphene content of 0.5%, the applied voltage of 18 KV, and the spinning flow rate of 0.12 μL/min.

Motile microorganisms hybrid nanoliquid flow with the influence of activation energy and heat source over a rotating disc

The present article examines the consequences of a magnetic field, Hall current, and thermal radiation on the spinning flow of hybrid nanofluid (HNF) across a revolving disc. The core objective of the study is to improve the energy transference rate through hybrid nano liquid for industrial and engineering operations. The HNFs have advanced thermophysical characteristics. Therefore, in the current study, a superior class of nanomaterials (carbon nanotubes (CNTs) and Al2O3) are added to the base fluid. The modeled equations are demoted to a dimensionless set of Ordinary differential equations (ODEs) through similarity conversion and are analytically solved by engaging the homotopy analysis method. The physical constraints’ effect on energy, velocity, motile microorganism, and mass profiles have been drawn and discussed. For accuracy, the results are compared to the published studies, which ensures the accuracy and reliability of the technique and results. It is observed that the energy communication rate lessens with the flourishing values of thermal radiation and for Hall current. Furthermore, it is noted that due to its carbon–carbon bonding in CNTs, it has a greater tendency for energy propagation than Al2O3 nanoparticles.

Emergence of large spin-charge interconversion at an oxidized Cu/W interface

Spin-orbitronic devices can integrate memory and logic by exploiting spin-charge interconversion (SCI), which is optimized by design and materials selection. In these devices, such as the magnetoelectric spin-orbit (MESO) logic, interfaces are crucial elements as they can prohibit or promote spin flow in a device as well as possess spin-orbit coupling resulting in interfacial SCI. Here, we study the origin of SCI in a Py/Cu/W lateral spin valve and quantify its efficiency. An exhaustive characterization of the interface between Cu and W electrodes uncovers the presence of an oxidized layer (WO$_x$). We determine that the SCI occurs at the Cu/WO$_x$ interface with a temperature-independent interfacial spin-loss conductance of $G_{||} \approx$ 20 $\times$ 10$^{13} \Omega^{-1}m^{-2}$ and an interfacial spin-charge conductivity $\sigma_{SC}=-$1610 $\Omega^{-1}cm^{-1}$ at 10 K ($-$830 $\Omega^{-1}cm^{-1}$ at 300 K). This corresponds to an efficiency given by the inverse Edelstein length $\lambda_{IEE}=-$0.76 nm at 10 K ($-$0.4 nm at 300 K), which is remarkably larger than in metal/metal and metal/oxide interfaces and bulk heavy metals. The large SCI efficiency at such an oxidized interface is a promising candidate for the magnetic readout in MESO logic devices.

Nontrivial effect of dephasing: Enhancement of rectification of spin current in graded XX chains.

In order to reveal mechanisms to control and manipulate spin currents, we perform a detailed investigation of the dephasing effects in the open XX model with a Lindblad dynamics involving global dissipators and thermal baths. Specifically, we consider dephasing noise modeled by current-preserving Lindblad dissipators acting on graded versions of these spin systems, that is, systems in which the magnetic field and/or the spin interaction are growing (decreasing) along the chain. In our analysis, we study the nonequilibrium steady state via the covariance matrix using the Jordan-Wigner approach to compute the spin currents. We find that the interplay between dephasing and graded systems gives rise to a nontrivial behavior: When we have homogeneous magnetic field and graded interactions we have rectification enhancement mechanisms, and when we have fully graded systems we can control the spin current in order to keep the direction of the particle and/or spin flow even with inverted baths. We describe our result in detailed numerical analysis and we see that rectification in this simple model indicates that the phenomenon may generally occur in quantum spin systems.

Spin-torque generation using a compositional gradient at the interface between titanium and tungsten thin films

We experimentally demonstrate spin-torque generation using a compositional gradient at the interface between titanium and tungsten thin films. The width of the compositional gradient interface (CGI) between films is varied from 1.4 to 2.0 nm via sputtering. Spin-torque ferromagnetic resonance is observed in the ferromagnetic ${\mathrm{Ni}}_{95}{\mathrm{Cu}}_{5}$ alloy fabricated on a Ti/W bilayer with the CGI. The positive spin torque increases with decreasing CGI width, but a negative spin torque is superimposed owing to the negative spin Hall effect in bulk tungsten. A structural undulation in the CGI eliminates this variation in positive spin torque. The CGI width dependence of the spin torque is associated with the generation of spin and/or orbital angular momentum flow at the CGI. Spin-torque generation using a CGI expands the range of material choice for magnetic nonvolatile memory applications.

Numerical solution of an electrically conducting spinning flow of hybrid nanofluid comprised of silver and gold nanoparticles across two parallel surfaces

The analysis of the energy transport mechanism received much attention from scientists and researchers. Conventional fluids like vegetable oils, water, ethylene glycol, and transformer oil play a vital role in numerous industrial activities. In certain industrial operations, the low heat conductivity of base fluids causes significant difficulties. This inevitably led to the advancement of critical aspects of nanotechnology. The tremendous significance of nanoscience is in improving the thermal transfer process in different heating transmitting equipment. Therefore, the MHD spinning flow of hybrid nanofluid (HNF) across two permeable surfaces is reviewed. The HNF is made of silver (Ag) and gold (Au) nanoparticles (NPs) in the ethylene glycol (EG). The modeled equations are non-dimensionalized and degraded to a set of ODEs through similarity substitution. The numerical procedure parametric continuation method (PCM) is used to estimate the 1st order set of differential equations. The significances of velocity and energy curves are derived versus several physical parameters. The results are revealed through Tables and Figures. It has been determined that the radial velocity curve declines with the varying values of the stretching parameter, Reynold number, and rotation factor while improving with the influence of the suction factor. Furthermore, the energy profile enhances with the rising number of Au and Ag-NPs in the base fluid.