Antiferromagnetic Coupling Research Articles

A doubly Phenoxyacetate-bridged dinuclear manganese(II) complex with 1,10-Phenanthroline: Synthesis, 1-D supramolecular structure, Hirshfeld surface analysis, magnetic and theoretical studies

We report herein the synthesis and characterization of [Mn2(POA)2(Phen)4](BF4)2·H2O, 1 where POA = phenoxyacetate; Phen = 1,10-phenthroline, respectively. The crystalline complex was obtained via slow evaporation at room temperature and characterized by single crystal X-ray diffraction. FTIR and UV–vis spectroscopy were utilized to elucidate the structure of the new compound. Complex 1 crystallizes in the monoclinic crystal system with space group P21/n. Hirshfeld surface analysis revealed various intermolecular interactions in the crystal lattice. Quantum Theory of Atoms in Molecules (QTAIM), Reduced Density Gradient (RDG), and Natural Bond Orbital (NBO) analyses were employed to investigate the diverse non-covalent interactions stabilizing the crystal structure. In complex 1, the BF4− counterion plays a crucial role in crystal assembly through a network of F···H C interactions with varying strengths governed by the interaction angle and consequent ellipticity. Additionally, B − F···π interactions were observed. Other interactions include weak-to-medium hydrogen bonds and π-interactions (CH···π and π···π) within the asymmetric units and dimers extracted from the unit cell. Notably, unconventional interactions were identified and characterized in complex 1, which is C H···π interactions with the σ(CH) orbital donating to an empty p orbital in the asymmetric unit of 1. Variable-temperature magnetic susceptibility data disclosed the occurrence of weak antiferromagnetic coupling within the doubly bridged manganese(II) core with a J value of – 2.11 cm−1.

Synthesis and characterization of two Cu(II) complexes with nicotinamide, oxalate, and nitrate as mixed ligands

A polynuclear Cu(II) coordination system of {[Cu(ox)(NA)]. H2O}n (1), where ox = oxalate and NA = nicotinamide, and a mononuclear compound [Cu(NA)2(NO3)2(H2O)2] (2) were synthesized and characterized by single-crystal X-ray diffraction (1), IR, UV–VIS and EPR spectra, magnetic measurements and elemental analysis. In both complexes, Cu(II) adopts a distorted octahedral geometry. In 1 each copper center is coordinated to two oxalate units: one in a bis (bidentate) chelating mode linking two metal ions from the same plane, while the other, through a µ 4 pattern, linking copper ions from adjacent positions. The sixth coordination position of each copper ion is occupied by the pyridinic nitrogen of a nicotinamide molecule. In 2 the Cu(II) basal plane consists of the oxygen atoms of the water molecules and the nitrogen atoms of nicotinamide molecules. The axial positions are occupied by oxygen atoms of the two nitrate groups, which are monodentate. The magnetic measurements for the polynuclear complex show antiferromagnetic coupling, the electronic structure modeling completing the insight to orbital factors of the spin interaction.

Synthesis, Structural Aspects, Magnetic, and Adsorption Properties of a Dinuclear Cu (II) Complex Derived From Mixed Ligand Approach

ABSTRACTA dinuclear copper complex, [Cu2(teaH)(pNBA)2(H2O)2]·MeOH·pNBH (1) (where teaH3 = triethanolamine, pNBH = 4‐nitro‐benzoic acid, and pNBA = 4‐nitro‐benzoate) has been prepared and structurally characterized. In 1, there is an interesting intermolecular structure that is shown as a tetramer copper connected in chain‐like motif. In the UV‐Vis spectrum, higher absorbance at 267 nm is referred to n → π* transition, coupled with a weak peak at 500 nm, indicating another transition, which is specified as metal‐to‐ligand charge transfer. The higher intensity peak in the photoluminescence spectrum is marked as the absorption of energy required for the excitation of electrons, whereas lower intensity peaks show the emission of energy, which describes d‐d transitions of Cu (II) electrons due to d9 configuration. Complex 1 was explored for the adsorption of methylene blue (MB) dye, with the maximum adsorption as 101.07 mg/g, whereas the removal efficiency was estimated to be 81.05%. In conformity with the kinetic studies, the adsorption process proceeded via a Pseudo‐first‐order kinetic model. The incorporation of mixed ligands such as teaH3 and pNBH in 1 tends to increase the dimensionality that led to increased MB adsorption. The plausible mechanism behind the adsorption was favored by hydrogen‐bonding, electrostatic, π–π, and n–π* interactions, operating between the dye and complex 1. Further, the H‐bonding and these interactions provided stability to the complex, and an improved dye adsorption was observed even during the 2nd and 3rd recyclability experiments. Additionally, complex 1 corroborated remarkable stability after dye adsorption, allowing for up to four recycling turns. The magnetic study revealed antiferromagnetic coupling between the two magnetic centers with a singlet ground state (S = 0).

Electric‐Field‐ and Stacking‐Tuned Antiferromagnetic FeClF Bilayer: The Coexistence of Bipolar Magnetic Semiconductor and Anomalous Valley Hall Effect

AbstractValley polarization from broken inversion symmetry provides a new degree of freedom for carriers, bipolar magnetic semiconductor (BMS) generates a purely spin‐polarized current under a gate voltage, but few systems possess the coexistence of valley polarization and BMS. Based on the recent experimental FeCl2 flakes, reversible electric‐field effect on the valley‐ and spin‐polarized Janus FeClF bilayer with different stackings are investigated herein. Janus FeClF bilayers in all three stacks possess interlayer antiferromagnetic (AFM) and intralayer ferromagnetic (FM) couplings. The most stable A (Cl‐Fe‐F‐Cl‐Fe‐F) stack possesses concurrent and spontaneous BMS nature and valley polarization with perpendicular magnetic anisotropy (PMA), while B (Cl‐Fe‐F‐F‐Fe‐Cl) and C (F‐Fe‐Cl‐Cl‐Fe‐F) stacks exhibit AFM semiconductor characters without valley polarization. Electric‐field achieves a transition of BMS and AFM semiconductor. Large ferrovalley (≈108 meV) exists and is mainly contributed by Fe‐dxy and orbitals. With the out‐of‐plane to in‐plane to out‐of‐plane transition of the easy axis, anomalous valley Hall effect (AVHE) can be manipulated to presence and disappearance by perpendicular electric‐field, indicating the valley switch effect (VSE). The coexisting BMS feature, PMA, AVHE and VSE make Janus FeClF bilayer a promising candidate for multifunctional valleytronic and spintronic applications, favoring broad explorations for the low‐dimensional Janus family.

Identifying Band Structure Changes of FePS3 across the Antiferromagnetic Phase Transition.

Magnetic 2D materials enable interesting tuning options of magnetism. As an example, the van der Waals material FePS3, a zig-zag-type intralayer antiferromagnet, exhibits very strong magnetoelastic coupling due to the different bond lengths along different ferromagnetic and antiferromagnetic coupling directions enabling elastic tuning of magnetic properties. The likely cause of the length change is the intricate competition between direct exchange of the Fe atoms and superexchange via the S and P atoms. To elucidate this interplay, we study the band structure of exfoliated FePS3 by μm scale ARPES (angular resolved photoelectron spectroscopy), both, above and below the Néel temperature TN. We found three characteristic changes across TN. They involve S 3p-type bands, Fe 3d-type bands and P 3p-type bands, respectively, as attributed by comparison with density functional theory calculations (DFT + U). This highlights the involvement of all the atoms in the magnetic phase transition providing independent evidence for the intricate exchange paths.

Structural Effect of N-7 Alkylation in 6-Chloropurine on Cu (II) Binding: Effect of Anions and Magnetic Studies.

This study investigates the anion-directed assembly of discrete copper (II) complexes. The ligands of choice are two N7-alkyl-purine-based neutral ligands. These ligands facilitate the exclusive coordination through the N3 and N9 positions, preventing polymeric chain formation. Perchlorate ions promoted the formation of discrete paddlewheel-like complexes with the general formula [Cu2(μ-Pur)4(CH3CN)2]4+, while chloride ions yielded chloride-bridged dimers of the form [Cu2(Pur)2(μ-Cl)2Cl2]. Copper-copper bond distances within these complexes ranged from 2.92 to 2.98 Å. Magnetic susceptibility measurement of chloride-bridged complexes exhibited antiferromagnetic coupling, whereas paddlewheel complexes displayed more complex alternating ferromagnetic and antiferromagnetic interactions. Chloride-bridged compounds exhibited strong near-infrared absorption.

Polarity-Reversal of Exchange Bias in van der Waals FePS3/Fe3GaTe2 Heterostructures.

Exchange bias (EB) in antiferromagnetic (AFM)/ferromagnetic heterostructures is crucial for the advancement of spintronic devices and has attracted significant attention. The common EB effect in van der Waals heterostructures features a low blocking temperature (Tb) and a single polarity. In this work, a significant EB effect with a Tb up to 150K is observed in FePS3/Fe3GaTe2 heterostructures, and in particular, the EB exhibits an unusual temperature-dependent polarity-reversal behavior. Under a high positive field-cooling condition (e.g., μ0H ≥0.5T), a negative EB field (HEB) is observed at low temperatures, and with increasing temperature, the HEB crosses zero at ≈20K, subsequently becomes positive and later approaches zero again at Tb. A model composed of a top FePS3/interfacial FePS3/Fe3GaTe2 sandwich structure is proposed. The charge transfer from Fe3GaTe2 to FePS3 at the interface induces net magnetic moments (∆M) in FePS3. The interface favors AFM coupling, and thus the reversal of ∆M of the interfacial FePS3 leads to the polarity-reversal of EB. Moreover, the EB can be extended to the bare Fe3GaTe2 region of the Fe3GaTe2 flake partially covered by FePS3. This work provides opportunities for a deeper understanding of the EB effect and opens a new route toward constructing novel spintronic devices.

The Role of Rare-Earth Atoms in the Anisotropy and Antiferromagnetic Exchange Coupling at a Hybrid Metal-Organic Interface.

Magnetic anisotropy and magnetic exchange interactions are crucial parameters that characterize the hybrid metal-organic interface, a key component of an organic spintronic device. It is shown that the incorporation of 4f RE atoms to hybrid metal-organic interfaces of CuPc/REAu2 type (RE = Gd, Ho) constitutes a feasible approach toward on-demand magnetic properties and functionalities. The GdAu2 and HoAu2 substrates differ in their magnetic anisotropy behavior. Remarkably, the HoAu2 surface promotes the inherent out-of-plane anisotropy of CuPc, owing to the match between the anisotropy axis of substrate and molecule. Furthermore, the presence of RE atoms leads to a spontaneous antiferromagnetic exchange coupling at the interface, induced by the 3d-4f superexchange interaction between the unpaired 3d electron of CuPc and the 4f electrons of the RE atoms. It is shown that 4f RE atoms with unquenched quantum orbital momentum ( ), as it is the case of Ho, induce an anisotropic interfacial exchangecoupling.

Large coercivity and enhanced magnetization in La-substituted Sm6Mn23 alloys

The magnetic properties of Sm6Mn23-based alloys are still not fully understood for their high complexity in magnetic and crystallographic structures. This work presents studies of the structure and magnetic properties of Sm6Mn23 and Sm5LaMn23 alloys. The results show that both the binary and La-substituted ternary alloys crystallize in a cubic Th6Mn23 type structure (Fm-3m) with trace amount of Mn impurities. The lattice parameter of Sm5LaMn23 is slightly larger than that of Sm6Mn23. The Curie temperature of Sm5LaMn23 is ∼403 K, which is lower than that of Sm6Mn23. A field-dependent magnetic transition was observed in Sm5LaMn23, which shows a decreasing temperature at which Sm5LaMn23 exhibiting maximal magnetization with increasing field, indicating a suppression of the antiferromagnetic coupling of the rare earth and Mn moments under applied field. Large coercivities up to 0.74 T and 1.2 T are observed in Sm5LaMn23 bulk alloys and powders, respectively. The saturate magnetization, the remanent magnetization, and the coercivity of Sm5LaMn23 at 5 K are much higher than that of Sm6Mn23. The ball-milled Sm5LaMn23 powders exhibit significantly enhanced coercivity and magnetization. The refinement of the grain size during ball-milling results in the enhanced coercivity. The magnetic purification of the powders and possible local ferromagnetic configuration of the surface Mn atoms may result in the enhanced magnetization.

An Organometallic Erbium Bismuth Cluster Complex Comprising a Bi66- Zintl Ion.

An organometallic erbium bismuth cluster complex, [K(THF)4]2[Cp*2Er2Bi6] (1), featuring a heterometallocubane core was isolated. The cube emerges from the rare Bi66- Zintl ion, bridging two erbium centers for the first time. SQUID magnetometry and ab initio calculations uncovered dominant antiferromagnetic coupling enabled through the chair-like hexabismuth anion. The gained insight will promote the design of future polynuclear magnetic molecules comprising prolate lanthanide ions.

Sr4Os3O12 – A Layered Osmate(V,VI) that is Magnetic Close to Room Temperature

AbstractBlack crystals of the mixed‐valence osmate(V,VI) Sr4Os3O12 were grown via a gas phase reaction in an evacuated silica tube. The material is attracted to a permanent magnet at room temperature (295±5 K) but loses this property when heated or cooled. In this temperature interval, soft magnetic behavior with vanishing coercivity is observed, but the saturation magnetization is only 0.05 μB per formula unit. Resistivity measurements show that Sr4Os3O12 is a semiconductor with a small band gap of about 0.26 eV at room temperature. X‐ray diffraction on a single‐crystal revealed a rhombohedral structure with the space group R m and lattice parameters ar=554.64(2) pm and cr=2700.1(1) pm at 300(1) K. The compound crystallizes in the La4Ti3O12 structure type and is isostructural to Sr4CoRe2O12. The structure is a rhombohedral stack of layered blocks, each of which can be considered as a section of three layers of the cubic perovskite structure cut perpendicular to one of its threefold axes. The Os–O−Os bond angle of about 175° favors superexchange that leads to antiferromagnetic coupling between the osmium atoms with 5d3 and 5d2 configurations. Sr4Os3O12 exhibits strong lattice dynamics. One aspect is the antiferro‐rotative lattice modes of the corner‐sharing [OsO6] octahedra, which freeze upon cooling. At 100 K, an ordered, yet twinned triclinic superstructure is formed. Strong spin‐orbit coupling and other effects cause deformations of the [OsO6] octahedra that differ significantly at 300 K and 100 K, suggesting a change in the electronic configuration. Competing ground states could also explain the temperature‐dependent band gap and the magnetic fluctuations manifested in the magnetization peak at room temperature.

Evidence of Spin Reorientation from Γ4 to Γ2 and Sign Reversal Exchange Bias in CeCrO3 Nanoparticles

Herein, the temperature‐dependent magnetic structure and sign reversal exchange bias in CeCrO3 using magnetization data and time‐of‐flight neutron diffraction data which is given less attention among RCrO3 are investigated. While nuclear structural analysis using Rietveld refinement exhibits distorted orthorhombic structure within Pnma space group, temperature dependence of the magnetic structure using neutron diffraction reveals possible spin configurations, namely, Γ4, Γ2, and Γ1, within the temperature range of 6–300 K. Temperature‐dependent magnetization shows compensation temperature, Tcomp, at 58 K, spin reorientation temperature, TSR, at 15 K along with a Neel temperature, TN, at 260 K which is the outcome of the competition between canted antiferromagnetic ordering of Cr3+ ions and Ce3+ ions in CeCrO3. Furthermore, the magnetization versus magnetic field (M vs H) measurements indicate transition of the Γ4 spin structure to Γ2 spin structure around TSR which is further supported by reversible‐to‐irreversible changes observed in temperature‐dependent MFCC and MFCW. Moreover, a temperature‐driven sign reversal of exchange bias in CeCrO3 is observed, resulting from the competition between antiferromagnetic coupling between chromium moment (MCr) and cerium moment (MCe) in these nanoparticles. This intriguing behavior holds significant potential for the development of thermally assisted magnetic random access memory.

Thermoelectric Performance in Triplet‐Ground‐State Polymer Intrinsically Boosted by Enhanced Proquinoidal Characteristic

AbstractOver the past decade, polymer thermoelectric materials featuring flexibility, lightness, and bio‐friendliness have been paid increasing attention as promising candidates for waste heat recovery and energy generation. For a long time, the dominant approach to optimizing the thermoelectric performance of most organic materials is chemical doping, which, however, is not always ideal for practical applications due to its tendency to involve intricate processing procedure and trigger material and device instability. Currently, the pursuit of single‐component neutral thermoelectric materials without exogenous doping presents a compelling alternative. In this work, we designed and synthesized a high‐spin polymer material, PBBT‐TT, by simultaneously employing thieno[3,4‐b]thiophene (TbT) and benzo[1,2‐c : 4,5‐c′]bis[1,2,5]thiadiazole (BBT) units with pronounced proquinoidal characteristics, its analogue, PBBT‐T to demonstrate the effect of the TbT unit was also synthesized. The results indicate that because of the enhanced quinoidal resonance, increased spin density and strong intermolecular antiferromagnetic coupling, PBBT‐TT exhibits high intrinsic electrical conductivity and Seebeck coefficient, which showcases an outstanding power factor of 26.1 μW m−1 K−2 without doping. This achievement surpasses other neutral organic conjugated polymer and radical conductors, and is even comparable to some typical early‐stage doped polymers. Notably, PBBT‐TT exhibits remarkable ambient stability, retaining its initial thermoelectric performance over a 120‐day period. Our finding demonstrates that modulating the intermolecular spin interactions in open‐shell polymers through the introduction of strong proquinoidal units is an effective strategy for the development of doping‐free, intrinsically high‐performance polymer thermoelectric materials.

Thermoelectric Performance in Triplet-Ground-State Polymer Intrinsically Boosted by Enhanced Proquinoidal Characteristic.

Over the past decade, polymer thermoelectric materials featuring flexibility, lightness, and bio-friendliness have been paid increasing attention as promising candidates for waste heat recovery and energy generation. For a long time, the dominant approach to optimizing the thermoelectric performance of most organic materials is chemical doping, which, however, is not always ideal for practical applications due to its tendency to involve intricate processing procedure and trigger material and device instability. Currently, the pursuit of single-component neutral thermoelectric materials without exogenous doping presents a compelling alternative. In this work, we designed and synthesized a high-spin polymer material, PBBT-TT, by simultaneously employing thieno[3,4-b]thiophene (TbT) and benzo[1,2-c : 4,5-c']bis[1,2,5]thiadiazole (BBT) units with pronounced proquinoidal characteristics, its analogue, PBBT-T to demonstrate the effect of the TbT unit was also synthesized. The results indicate that because of the enhanced quinoidal resonance, increased spin density and strong intermolecular antiferromagnetic coupling, PBBT-TT exhibits high intrinsic electrical conductivity and Seebeck coefficient, which showcases an outstanding power factor of 26.1 μW m-1 K-2 without doping. This achievement surpasses other neutral organic conjugated polymer and radical conductors, and is even comparable to some typical early-stage doped polymers. Notably, PBBT-TT exhibits remarkable ambient stability, retaining its initial thermoelectric performance over a 120-day period. Our finding demonstrates that modulating the intermolecular spin interactions in open-shell polymers through the introduction of strong proquinoidal units is an effective strategy for the development of doping-free, intrinsically high-performance polymer thermoelectric materials.

Tuning the magnetic properties of ultrathin magnetic films with MgO as the buffer layer

To minimize the screening effect of a metallic ferromagnetic film and improve the effectiveness of electric field modulation, high-quality ultrathin magnetic film is one of the critical prerequisites. Here ultrathin magnetic films and synthetic antiferromagnetics (SAFs) are deposited on SiO2 substrates at room temperature using the magnetron sputtering. Atomic force microscopy is used to characterize the roughness of MgO, Nb, Ru, W, and CoFeB films, revealing their atomic-level flatness, with root mean square roughness values below 0.3 nm, which are crucial in the subsequent preparation of ultrathin SAF to achieve high-quality interfaces. The results from the magneto-optical Kerr microscopy suggest that when MgO is 1.48 nm, ultrathin 0.6 nm CoFeB exhibits stable room-temperature perpendicular magnetic anisotropy (PMA) and there is a correlation between room-temperature ferromagnetism and MgO thickness. For SAFs, ultrathin 0.6 nm CoFeB-based SAF exhibits room-temperature antiferromagnetism via the Ruderman-Kittel-Kasuya-Yosida interaction mechanism. The exchange coupling field demonstrates that the transition between ferromagnetic coupling and antiferromagnetic coupling can be regulated by adjusting both the thickness of the non-magnetic spacer layer and the CoFeB layer. This work lays the ground for the potential applications of high-density storage and efficient electric field modulation of ferromagnetic multilayers for improving energy efficiency.

Origin of magnetism via cation vacancy defects in non-stoichiometric NiCo2O4 nanoparticles: A synchrotron-based x-ray absorption and x-ray magnetic circular dichroism spectroscopic study

The present study probes the effect of cation distributions in the structural, optical, electronic, and magnetic properties of mixed-valent inverse-spinel NiCo2O4 (NCO) nanoparticles (NPs). NCO NPs were prepared using the sol–gel combustion method and the grain size was obtained in the magnetic exchange length range assumed to be from single-ion anisotropy. The Raman and photoluminescence spectroscopies confirm the presence of an inverse-spinel structure with different oxidation states, and vibrating sample magnetometry clarifies the existence of ferromagnetism with the presence of magnetic anisotropy among the cations. These NPs annealed at a higher grain-growth temperature accumulate ferrimagnetic properties and produce magneto-crystalline anisotropy making NCO an assuring material for spintronic applications. A detailed x-ray absorption spectroscopy and x-ray magnetic circular dichroism studies reveal an indestructible correlation between the distribution of the present cations and the element-specific origin of ferrimagnetic behavior. Ni is found to be accountable for the magnetic moment and electronic conduction, whereas Co is associated mainly with the generation of the magnetic anisotropy even in the polycrystalline NP form. This describes the anti-ferromagnetic coupling between Co and Ni ions that is pivotal in demonstrating the exchange interaction between these cations. The above result signifies the site-dependent cation valence states for the magnetic properties, and the extent of growing conditions are related to such cation-site dysfunction. This depicts further tunability in NCO as a functional oxide material.

Synthesis, crystallographic, spectroscopic, magnetic, and DFT characterization of a new strandberg-type polyoxometalate: (H2AEP)4[CoP2Mo5]2 ̶ first principles calculations

This work reports the synthesis of a novel diphosphopentamolybdate compound with the formula (C6H17N3)4[Co(H2O)4P2Mo5O23]2‧8·74H2O abbreviated as (H2AEP)4[CoP2Mo5]2. Characterization of this compound was carried out using various techniques, including X-ray diffraction, thermal analysis (TGA), and spectroscopies such as FT-IR, Raman, UV–visible, and fluorescence. The structural study reveals that the studied material crystallizes in the orthorhombic system Pca21 with lattice parameters of a = 18.6348(16) Å, b = 11.8613(10) Å, c = 35.074(3) Å, and volume V = 7752.5(11) Å3, and a number of formula units per primitive cell Z = 4. The crystal structure study reveals that the Strandberg anions (P2Mo5O23)6− are connected to Co(II) octahedra through the terminal oxygen atoms of the PO4 tetrahedra, creating 1-D anionic chains in the crystallographic direction [101]. The 1-(2-Aminoethyl)piperazinium (AEP) cations are located within the anionic framework to neutralize its negative charge. The magnetic characteristics of the compound were investigated by examining the temperature-dependent molecular susceptibility over the range of 2–300 K. The analysis revealed the presence of an antiferromagnetic exchange interaction. Moreover, the material's refractive index exhibited significant dispersive behavior within the visible spectrum, indicating its potential for use in visible optical communication devices. A first-principles density functional theory (DFT)-based computational study confirms the semiconducting behavior of (H2AEP)4[CoP2Mo5]2, revealing that in the ground state, high-spin octahedrally coordinated Co2+ cations exhibit a very weak antiferromagnetic coupling along the [Co(H2O)4P2Mo5O23]∞4−chains running in the crystal a direction.

Driving skyrmions in flow regime in synthetic ferrimagnets

The last decade has seen significant improvements in our understanding of skyrmions current induced dynamics, along with their room temperature stabilization, however, the impact of local material inhomogeneities still remains an issue that impedes reaching the regime of steady state motion of these spin textures. Here, we study the spin-torque driven motion of skyrmions in synthetic ferrimagnetic multilayers with the aim of achieving high mobility and reduced skyrmion Hall effect. We consider Pt|Co|Tb multilayers of various thicknesses with antiferromagnetic coupling between the Co and Tb magnetization. The increase of Tb thickness in the multilayers reduces the total magnetic moment and increases the spin-orbit torques allowing to reach velocities up to 400 ms−1 for skyrmions with diameters of about 160 nm. We demonstrate that due to reduced skyrmion Hall effect combined with the edge repulsion of the magnetic track, the skyrmions move along the track without any transverse deflection. Further, by comparing the field-induced domain wall motion and current-induced skyrmion motion, we demonstrate that the skyrmions at the largest current densities present all the characteristics of a dynamical flow regime.

N-Heterocyclic Carbene-Derived Carbon Disulfide Radical Ligands for Palladium Diradicals.

N-heterocyclic carbenes (NHCs) are recognized for their ability to stabilize various main group radicals; however, NHC-derived, sulfur-based radicals remain rare. In this study, we successfully synthesized and characterized a series of palladium diradical complexes that featured new sulfur-based radical ligands from NHC-carbon disulfide adducts. Spectroscopic and computational characterizations of the palladium complexes confirmed the open-shell singlet ground state, which resulted from the antiferromagnetic coupling of two unpaired electrons on each ligand. Proton nuclear magnetic resonance relaxometry was used to experimentally confirm the presence of these unpaired electrons. Moreover, the redox behavior of the complexes was localized on the ligand center, confirming the redox activity of the ligands. The discovery of this sulfur-based, redox-active radical ligand underscores the versatility and significance of NHC-derived radicals, thereby expanding the repertoire of radical ligands and opening new avenues for advanced material and catalytic systems.

Magnetic and thermodynamic properties of mixed spin-3/2 and spin-3 Ising ferrimagnets on a 2D triangular lattice: Monte Carlo study

Monte Carlo methods in the presence and absence of an external magnetic field were used to investigate the thermodynamic and magnetic properties of the mixed spins (3/2, 3) Ising ferrimagnets in a 2D triangular lattice consisting of sublattices A, B, and C. Two types of mixing were considered: S→=(SA,SB,SC)=(3/2,3,3) (Model I) and S→=(SA,SB,SC)=(3/2,3,3/2) (Model II). In contrast to bipartite lattices, the antiferromagnetic coupling between spin-3/2 and spin-3 in the triangular lattice leads to geometric frustrations that impact magnetic properties. Determination of ground state phase diagrams, combined with verification of whether or not there was magnetic hysteresis when crossing each transition line, revealed first- and second-order phase transition lines, as well as multicritical points. The temperature investigation in the absence of an external magnetic field revealed rich magnetic properties such as 1st- and 2nd-order phase transitions, N- and L-type compensation points, tricritical points, and critical endpoints, as well as M-, P-, Q-, R- and S-type total magnetization behaviours. The effect of the crystal field on finite-temperature phase diagrams and compensation behaviour was also carried out. As a result, the critical temperatures of Model II become constant when the crystal field is sufficiently strong. In contrast, several critical values of the crystal field for which the critical temperature is zero were identified for Model I. In the presence of a magnetic field, hysteresis behaviour and associated magnetic properties such as coercivity and magnetic remanence were investigated. The effect of crystal field and temperature was explored. Hysteresis of one to four loops were found at low temperatures when the crystal field varied. Finally, as the temperature rises, the hysteresis loops' area decreases to zero at high temperatures.