High Spin Research Articles

Electron Spin Polarization and Memory Effect in Supramolecular Gel Exclusively From Achiral Building Blocks.

Chirality has been identified as a crucial component in achieving high spin selectivity in organic polymers and π-conjugated molecules. In particular, chiral polymers and supramolecular structures have emerged as promising candidates for spin filtering due to the chirality-induced spin selectivity (CISS) effect. However, the CISS effect in supramolecular systems has not been extensively investigated, despite its potential for applications in spintronics. In this work, for the first time, the potential applications of the CISS effect in supramolecular gel materials and shed light on its untapped possibilities have been successfully explored. The ability of supramolecular gel exclusively made from achiral building blocks to selectively filter electron's spin through the symmetry breaking has been demonstrated. Furthermore, this study shows that their spin filtering efficacy can be improved by using chiral solvents. More importantly, the CISS effect has been employed to explore a novel phenomenon referred to as the "spin memory effect", where the desired spin information is preserved by retaining the helicity even in the absence of the chiral solvent. These findings underscore the immense potential for spintronics applications that rely solely on achiral components, thereby paving the way for new possibilities in device design and functionality.

On the Ionization Tolerance of C20 Fullerene in Ground and Excited Electronic States in Planetary Nebulae

As the smallest member of the fullerene family, C20 is yet to be discovered in planetary nebulae. In this work, we present a quantum chemical study via density functional theory (DFT) and partially by the MP2 on the ionization tolerance of this molecule in the space environment. Considering that the ionization and excitation phenomena play key roles in demonstrating the lifetime of a molecule, we examined both ground and excited electronic-state potential energy surfaces (PES) of C20 and its cations C20q+. Our theoretical results indicate that the C20 cage tolerates a positive charge as high as 13+ by characterizing local minimum geometries on both the abovementioned electronic states. The results are backed by characterizing both C2012+ and C2013+ as local minimum geometries at the MP2 level of computations. We also explored, theoretically and systematically, scenarios in which the electronic structure of neutral C20 is excited to very high spin multiplicity (beyond triplet state), and local minimum molecular geometries with cage structures are well characterized. We anticipate that such structural resistance to excitation and ionization delivers a prolonged lifetime necessary for the spectroscopic detection of this interesting molecule and its cations in space and potentially in planetary nebulae (PN).

Rewriting History in Integrable Stochastic Particle Systems

Many integrable stochastic particle systems in one space dimension (such as TASEP—Totally Asymmetric Simple Exclusion Process—and its q-deformation, the q-TASEP) remain integrable if we equip each particle with its own speed parameter. In this work, we present intertwining relations between Markov transition operators of particle systems which differ by a permutation of the speed parameters. These relations generalize our previous works (Petrov and Saenz in Probab Theory Relat Fields 182:481–530, 2022), (Petrov in SIGMA 17(021):34, 2021), but here we employ a novel approach based on the Yang-Baxter equation for the higher spin stochastic six vertex model. Our intertwiners are Markov transition operators, which leads to interesting probabilistic consequences. First, we obtain a new Lax-type differential equation for the Markov transition semigroups of homogeneous, continuous-time versions of our particle systems. Our Lax equation encodes the time evolution of multipoint observables of the q-TASEP and TASEP in a unified way, which may be of interest for the asymptotic analysis of multipoint observables of these systems. Second, we show that our intertwining relations lead to couplings between probability measures on trajectories of particle systems which differ by a permutation of the speed parameters. The conditional distribution for such a coupling is realized as a “rewriting history” random walk which randomly resamples the trajectory of a particle in a chamber determined by the trajectories of the neighboring particles. As a byproduct, we construct a new coupling for standard Poisson processes on the positive real half-line with different rates.

Co‐crystallization as a Strategy for Tuning Spin Crossover Properties of Mononuclear Mn(III) Schiff‐base Complexes

AbstractWe present co‐crystallization as an approach to tuning spin crossover (SCO) properties of mononuclear Mn(III) Schiff‐base complexes. Complexes [Mn(5‐F‐sal‐N‐1,5,8,12)]ClO4 ⋅ 0.5carbazole (cocrystal 1 a) and [Mn(5‐F‐sal‐N‐1,5,8,12)]PF6 ⋅ 0.5carbazole (cocrystal 2 b) are synthesized by the co‐crystallization of their parent complexes ( [Mn(5‐F‐sal‐N‐1,5,8,12)]Y, Y=ClO4− (1); Y=PF6− (2) ) with the carbazole and they both exhibit HS electronic configurations between 2 and 300 K. While, the parent complex 1 shows a nearly complete SCO with T1/2=100 K and complex 2 maintains a high‐spin (HS) state. The introduction of carbazole as the third component has a great influence on cation‐anion crystal packing and finally the cooperative effects of the SCO complexes.

Formation of wind-fed black hole high-mass X-ray binaries: The role of Roche-lobe-overflow post black hole formation

The three dynamically confirmed wind-fed black hole high-mass X-ray binaries (BH-HMXBs) are suggested to all contain a highly spinning black hole (BH). However, based on the theories of efficient angular momentum transport inside the stars, we expect that the first-born BHs in binary systems should have low spins, which is consistent with gravitational-wave observations. As a result, the origin of the high BH spins measured in wind-fed BH-HMXBs remains a mystery. In this paper, we conduct a binary population synthesis study on wind-fed BH-HMXBs at solar metallicity with the use of the newly developed code POSYDON odot $ are prevalent, posing a challenge in explaining simultaneously all observed properties of the BH-HMXB in our Galaxy, Cygnus X-1, and potentially hinting that the accretion efficiency onto non-degenerate stars, before the formation of the BH, is also more conservative than assumed in our simulations.

Isolated spin polarized hydrogen atoms as targets for laser-induced polarized electron acceleration

High density Spin Polarized Hydrogen (SPH) atoms, which can be prepared using UV dissociation of hydro-halide molecules, can be attractive as potential targets for laser ionization/acceleration schemes aiming to create high energy and high current polarized electron beams. However, for these SPH targets to be of practical use, they have to be spatially isolated from the halide atoms which accompany hydrogen in the parent hydro-halide molecule. We show how the UV dissociation dynamics of hydro-halides and the dissociation geometry and timing can be combined to prepare a variety of isolated SPH targets aimed to accommodate laser acceleration schemes.

Black hole spin evolution across cosmic time from the NewHorizon simulation

ABSTRACT Astrophysical black holes (BHs) have two fundamental properties: mass and spin. While the mass-evolution of BHs has been extensively studied, much less work has been done on predicting the distribution of BH spins. In this paper, we present the spin evolution for a sample of intermediate-mass and massive BHs from the NewHorizon simulation, which evolved BH spin across cosmic time in a full cosmological context through gas accretion, BH–BH mergers and BH feedback including jet spindown. As BHs grow, their spin evolution alternates between being dominated by gas accretion and BH mergers. Massive BHs are generally highly spinning. Accounting for the spin energy extracted through the Blandford–Znajek mechanism increases the scatter in BH spins, especially in the mass range $10^{5}{-}10^{7}\,\rm M_\odot$, where BHs had previously been predicted to be almost universally maximally spinning. We find no evidence for spin-down through efficient chaotic accretion. As a result of their high spin values, massive BHs have an average radiative efficiency of $\lt \varepsilon _{\rm r}^{\rm thin}\gt \approx 0.19$. As BHs spend much of their time at low redshift with a radiatively inefficient thick disc, BHs in our sample remain hard to observe. Different observational methods probe different sub-populations of BHs, significantly influencing the observed distribution of spins. Generally, X-ray-based methods and higher luminosity cuts increase the average observed BH spin. When taking BH spin evolution into account, BHs inject, on average, between three times (in quasar mode) and eight times (in radio mode) as much feedback energy into their host galaxy as previously assumed.

Ultra-low Gilbert damping and self-induced inverse spin Hall effect in GdFeCo thin films

Ferrimagnetic materials have garnered significant attention due to their broad range of tunabilities and functionalities in spintronics applications. Among these materials, rare earth-transition metal GdFeCo alloy films have been the subject of intensive investigation due to their spin-dependent transport properties and strong spin–orbit coupling. In this report, we present self-induced spin-to-charge conversion in single-layer GdFeCo films of different thicknesses via an inverse spin Hall effect. A detailed investigation of spin dynamics was carried out using broadband ferromagnetic resonance measurements. The anisotropy constant and the effective g-factor are found to decrease with thickness, and they become nearly constant for thicknesses beyond 25 nm. A remarkably low damping constant of 0.0029 ± 0.0003 is obtained in the 43 nm-thick film, which is the lowest among all previous reports on GdFeCo thin films. Furthermore, we have demonstrated a self-induced inverse spin Hall effect, which has not been reported so far in a single-layer of GdFeCo thin films. Our analysis shows that the inverse spin Hall effect becomes increasingly dominant over the spin rectification effect with increasing film thickness. The in-plane angular-dependent voltage measurement of the 43 nm-thick film reveals a spin pumping voltage of 1.64 μV. The observation of spin-to-charge current conversion could be due to the high spin–orbit coupling element Gd in the film as well as the interface between GeFeCo/Ti and substrate/GdFeCo of the films. Our findings underscore the potential of GdFeCo as a prime ferrimagnetic material for emerging spintronic technologies.

Nearly perfect spin polarization of noncollinear antiferromagnets

Ferromagnets with high spin polarization are known to be valuable for spintronics—a research field that exploits the spin degree of freedom in information technologies. Recently, antiferromagnets have emerged as promising alternative materials for spintronics due to their stability against magnetic perturbations, absence of stray fields, and ultrafast dynamics. For antiferromagnets, however, the concept of spin polarization and its relevance to the measured electrical response are elusive due to nominally zero net magnetization. Here, we define an effective momentum-dependent spin polarization and reveal an unexpected property of many noncollinear antiferromagnets to exhibit nearly 100% spin polarization in a broad area of the Fermi surface. This property leads to the emergence of an extraordinary tunneling magnetoresistance (ETMR) effect in antiferromagnetic tunnel junctions (AFMTJs). As a representative example, we predict that a noncollinear antiferromagnet Mn3GaN exhibits nearly 100% spin-polarized states that can efficiently tunnel through low-decay-rate evanescent states of perovskite oxide SrTiO3 resulting in ETMR as large as 104%. Our results uncover hidden functionality of material systems with noncollinear spin textures and open new perspectives for spintronics.

Coordination Induced Spin State Transition Switches the Reactivity of Nickel (II) Porphyrin in Hydrogen Evolution Reaction

AbstractElectron spin plays a critical role in chemical processes, particularly in reactions involving metal complexes with unpaired electrons. However, more definitive state‐to‐state experiments are needed to better elucidate the role of electronic spin. Herein, we chose nickel (II) 5,10,15,20‐tetrakis(pentafluorophenyl) porphyrin 1 as a catalyst, which allows switching from a low spin to a high spin state of Ni (II) center through an axial pyridine coordination, for electrocatalytic hydrogen evolution reaction (HER). When pyridine is present, we observed β‐hydrogenation of porphyrin through electron transfer followed by proton transfer. In contrast, hydrogen evolution mainly occurs via the concerted proton‐coupling electron transfer without pyridine coordination. Similar distinct spin‐dependent selectivity was also observed in chemical reduction of 1 by CoCp2 with subsequent addition of pyridinium p‐toluenesulfonate. Computational calculations using density functional theory demonstrated that the transition from low spin to high spin state enriches the ligand's electron density after one‐electron reduction, leading to preferential protonation of β‐periphery rather than meso‐position or metal center.

Coordination Induced Spin State Transition Switches the Reactivity of Nickel (II) Porphyrin in Hydrogen Evolution Reaction.

Electron spin plays a critical role in chemical processes, particularly in reactions involving metal complexes with unpaired electrons. However, more definitive state-to-state experiments are needed to better elucidate the role of electronic spin. Herein, we chose nickel (II) 5,10,15,20-tetrakis(pentafluorophenyl) porphyrin 1 as a catalyst, which allows switching from a low spin to a high spin state of Ni (II) center through an axial pyridine coordination, for electrocatalytic hydrogen evolution reaction (HER). When pyridine is present, we observed β-hydrogenation of porphyrin through electron transfer followed by proton transfer. In contrast, hydrogen evolution mainly occurs via the concerted proton-coupling electron transfer without pyridine coordination. Similar distinct spin-dependent selectivity was also observed in chemical reduction of 1 by CoCp2 with subsequent addition of pyridinium p-toluenesulfonate. Computational calculations using density functional theory demonstrated that the transition from low spin to high spin state enriches the ligand's electron density after one-electron reduction, leading to preferential protonation of β-periphery rather than meso-position or metal center.

Symmetric vs. chiral approaches to massive fields with spin

Abstract Massive higher spin fields are notoriously difficult to introduce interactions when they are described by symmetric (spin)-tensors. An alternative approach is to use chiral description that does not have unphysical longitudinal modes. For low spin fields we show that chiral and symmetric approaches can be related via a family of invertible change of variables (equivalent to parent actions), which should facilitate introduction of consistent interactions in the symmetric approach and help to control parity in the chiral one. We consider some examples of electromagnetic and gravitational interactions and their transmutations when going to the chiral formulation. An interesting feature of the relation is how second class constraints get eliminated while preserving Lorentz invariance.

(General Student Poster Award Winner, 2nd Place) Understanding the Unique Phase Evolution of Prussian White Cathodes Mediated by the Intrainteraction in Hexacyanometallate Complexes

Transition metal–based Prussian whites (TM-PWs), consisting of a cyanide anion ((–C≡N–)−) and TM cations in an alternative manner, have a general chemical formula of AxTMm+TMn+(CN)6. PWs are characterized by the TM electronic states that exclusively adopt low spin (LS) toward the C atom and high spin (HS) toward the N atom through the hybridized covalent bonding in the TM–C≡N–TM unit. This property would significantly affect the phase transition behavior upon the release and storage of carrier ions; however, there have been only few studies on their associated features.In this talk, TM-PWs with different HS TM ions (Fe, Co, and Ni) were synthesized via co-precipitation and the phase transition behavior controlled by the π electron interaction between the cyanide anions and TM ions during battery operations was investigated. In situ X-ray diffraction and X-ray absorption fine structure analyses reveal that the combined effect of π bonding between metal and ligand effectively controls the bond length of the TM–C≡N–TM unit, thus influencing the lattice volume of TM-PW cathodes during the charge/discharge process. This study presents a comprehensive understanding of the structure–property relationship of the TM-PW cathodes involving π electron interactions during battery operations.

Physicochemical properties of La0.5Ba0.5Co1-xFexO3-δ (0 ≤ x ≤ 1) as positrode for proton ceramic electrochemical cells

Physicochemical properties of La0.5Ba0.5Co1-xFexO3-δ (0 ≤ x ≤ 1) as positrode for proton ceramic electrochemical cells

Enhancing Oxygen Catalytic Performance in Zinc-Air Batteries through Localized Micro-Interface Reconstruction of Cobalt-Manganese Spinel

Reversible zinc-air batteries are widely regarded as one of the most promising candidates for clean energy conversion and storage technology owing to their cost-effectiveness, inherent safety, wide operating temperature window and high theoretical energy density.(1) In general, the performance of zinc-air batteries is heavily dependent on highly active bifunctional electrocatalysts, which effectively accelerate oxygen reduction/evolution reaction (ORR/OER) kinetics. Among various electrocatalysts for advanced air cathodes, multivalent Co3-xMnxO4±δ oxides, as the representative mixed transition metal spinel, have attracted widespread interest because of their O2 catalytic potential and diverse properties.(2) In comparison to the state-of-the-art Pt- and Ir-based catalysts, the catalytic performances of Co3-xMnxO4± δ remains constrained by its low electrical conductivity and inadequate ability to adsorb and activate O2.(3) Herein, we develop a unique pathway to achieve the self-reconstruction of the local micro-interface and electronic structure of Co3-xMnxO4±δ via a combustion reaction coupled with a high-temperature reduction process. The Co particles derived from the self-reconstructed Cox@Co1.5-xMn1.5O4-δ catalyst not only facilitate the formation of a metal/oxide heterojunction active interface but also improve the electrical conductivity. More importantly, Co metal precipitated from the tetrahedral site with high spin electronic configuration induces the transformation of lattice oxygen into oxygen vacancies, thereby effectively accelerating reactant adsorption. As expected, the Cox@Co1.5-xMn1.5O4-δ catalyst shows good ORR/OER activity with low overpotential. Furthermore, the zinc-air battery assembled by Cox@Co1.5-xMn1.5O4-δ catalyst demonstrates an extended charge-discharge lifespan exceeding 1000 hours, significantly surpassing that of the Pt/C+Ir/C catalyst (100 hours). The primary factor contributing to its high stability is the dimensional growth following catalyst reconstitution. This work offers novel insights into enhancing the small molecule electrocatalytic performance of typical mixed transition metal oxides, including spinel and perovskite catalysts.References A. Li, S. Kong, C. Guo, H. Ooka, K. Adachi, D. Hashizume, Q. Jiang, H. Han, J. Xiao and R. Nakamura, Nature Catalysis, 5, 109 (2022).N. Xu, Y. Zhang, M. Wang, X. Fan, T. Zhang, L. Peng, X.-D. Zhou and J. Qiao, Nano Energy, 65, 104021 (2019).C. Li, X. Han, F. Cheng, Y. Hu, C. Chen and J. Chen, Nature Communications, 6, 7345 (2015).

Hyaluronic acid-based hydrogels as codelivery systems: The effect of intermolecular interactions investigated by HR-MAS and solid-state NMR Spectroscopy

Hydrogels based on hyaluronic acid and agarose-carbomer, due to their peculiar 3D architecture and biocompatibility, are promising candidates for pharmaceutical strategies based on the codelivery of drugs targeting different diseases. The successful development of these applications requires a precise understanding of drug-drug interactions and their effects on transport and release mechanisms. In this study, such an investigation is carried out on hydrogels loaded with ethosuximide and sodium salicylate at different concentrations. Intermolecular interactions and transport properties are characterized by means of High Resolution Magic Angle Spinning and solid-state Magic Angle Spinning NMR Spectroscopy. At variance with our previous findings on single-drug formulations, the two drugs exhibit closely similar diffusion patterns when co-loaded in the HA-based hydrogels, plausibly due to drug-drug intermolecular interactions. At the highest drug concentrations, where superdiffusion comes into play, we find a fraction of molecules with time-varying diffusion coefficients. A trapping-release mechanism is proposed to explain this observation, which also accounts for the role of drug-hydrogel interactions in drug diffusion motion. The effects of drug-drug interactions on release profiles are finally assessed by means of in vitro release experiments.

Impact of modified spin coating variations on electrical resistivity and UV detector responsivity in Mg-doped ZnO thin films

Impact of modified spin coating variations on electrical resistivity and UV detector responsivity in Mg-doped ZnO thin films

Facile Approach for the Fabrication of Vapor Sensitive Spin Transition Composite Nanofibers

AbstractIn this work polymer nanofibers were functionalized by incorporation of the spin transition (ST) compound [Fe(H2btm)2(H2O)2]Cl2 (FeH2btm) (H2btm=di(1H‐tetrazol‐5‐yl)methane). FeH2btm is an interesting compound due to its ability to reversibly and sensitively switch between high spin (HS) and low spin (LS) state when exposed to common volatile compounds (VOC) like ammonia and methanol. By using polyvinylidene fluoride (PVDF) as the main compound, inhibiting interactions between the complex and polymer were minimized. By using UV‐Vis spectroscopy, the visible and reversible switching between HS and LS state when exposed to an ammonia or hydrochloric acid atmosphere was confirmed. Powder X‐Ray diffraction (PXRD), scanning electron microscopy (SEM) and energy dispersive X‐Ray spectroscopy (EDX) show a homogenous distribution of FeH2btm with no major crystalline accumulations and a mean fiber diameter of 106±20 nm. The composite fiber has a similarly high thermal stability as the pure FeH2btm, as shown by thermogravimetric analysis (TGA). Mössbauer spectroscopy indicates an incomplete spin transition after exposition to ammonia. This could be due to low permeability of the VOC into the composite fiber.

The Effect of the Surrounding Matrix on Spin Transition Nanoparticles: How Shell Characteristics Alter Core Elastic Properties in Core‐Shell Particles

AbstractA surrounding matrix is known to alter nanoparticle spin transitions, the solid state structural phase changes associated with transitions between high spin (HS) and low spin(LS) states. To better quantify how the spin transition solid and surrounding matrix interact, several series of core‐shell particles were prepared based on RbxCo[Fe(CN)6]z ⋅ nH2O, RbCoFe‐PBA, as spin transition core with isostructural shells of different compositions and thicknesses. Synchrotron PXRD through the thermal high HS to LS, the LS to photoexcited high spin (PXHS), and thermal PXHS to LS transitions, show the activation energy is lowered as shells become thicker and stiffer. Calorimetry data coupled with transition state theory analysis indicate the core stiffens in the core‐shell particles relative to the uncoated particles. The conclusion is supported by microstrain analysis that shows stiffer shells limit the extent to which the core distorts as individual sites transition, leading to the lower activation energy. Finally, differences in lattice mismatch with different shell materials are shown to alter the mechanism by which the transition progresses.

Modification of the Spin Transition Properties in Hetero‐Anionic Iron(II)‐Triazole Complexes

AbstractThe phenomenon which is called spin crossover is known to occur in some coordination compounds with an octahedral ligand field and electron configurations from 3d4 to 3d7. Thereby, a reversible transition between spin states (high spin and low spin state) is possible, through several external stimuli. Iron(II) triazole complexes exhibit this phenomenon at a wide range of temperatures depending on the ligands and anions used. For this reason, they are often considered for several possible practical applications. It is also possible to combine ligands or anions to modify the transition temperature. The latter of which was rarely discussed in the past. In this study we synthesized a series of iron(II)‐4‐Aminotriazole complexes, with different ratios of chloride‐ and tetrafluoroborate‐anions, of the formula [Fe(Atrz)3]Cl2−X(BF4)X. We show that the combination of these anions leads to transition temperatures between those of their corresponding pure anion complexes. We furthermore present that a simple modification of the synthesis leads to a possible easy way of fine‐tuning transitions temperatures.