Search Results (227)

Noncoplanar spin textures give rise not only to unusual magnetic structures but also to emergent electromagnetic responses stemming from scalar spin chirality, such as the topological Hall effect. In this study, we theoretically investigate nonreciprocal transport phenomena induced by noncoplanar magnetic orderings through microscopic model analyses. By focusing on meron–antimeron spin textures that exhibit local scalar spin chirality while maintaining vanishing global chirality, we demonstrate that the electronic band structure becomes asymmetrically modulated, which leads to the emergence of nonreciprocal transport. The present mechanism arises purely from the noncoplanar magnetic texture itself and requires neither net magnetization nor relativistic spin–orbit coupling. We further discuss the potential relevance of our findings to the compound Gd₂PdSi₃, which has been suggested to host a meron–antimeron crystal phase at low temperatures. Full article

Magnetic nanowires with domain walls (DWs) play a crucial role in the advancement of next-generation memory and spintronic devices. Understanding the thermal effects on domain wall behavior is essential for optimizing performance and stability. This study investigates the thermal chirality-dependent dynamics and pinning of transverse domain walls (TDWs) in Z-junction nanowires using micromagnetic simulations. The analysis focuses on head-to-head (HHW) and tail-to-tail (TTW) domain walls with up and down chirality under varying thermal conditions. The results indicate that higher temperatures reduce the pinning strength and depinning current density, leading to enhanced domain wall velocity. At 200 K, the HHW_down domain wall depins at a critical current density of 1.2 × 10¹¹ A/m², while HHW_up requires a higher depinning temperature, indicating stronger pinning effects. Similarly, the depinning temperature (T_d) increases with Z-junction depth (d), reaching 300 K at d = 50 nm, while increasing Z-junction (λ) weakens pinning, reducing T_d to 150 K at λ = 50 nm. Additionally, the influence of Z-junction geometry and magnetic properties, such as saturation magnetization (M_s) and anisotropy constant (K_u), is examined to determine their effects on thermal pinning and depinning. These findings highlight the critical role of chirality and thermal activation in domain wall motion, offering insights into the design of energy-efficient, high-speed nanowire-based memory devices. Full article

We investigate magnetic instabilities toward multiple-Q states in centrosymmetric bilayer triangular-lattice systems. By focusing on the interplay between the layer-dependent Dzyaloshinskii–Moriya interaction and layer-independent bond-dependent anisotropic interaction, both of which originate from the relativistic spin-orbit coupling, we construct a low-temperature phase diagram based on an effective spin model that also includes frustrated isotropic exchange interactions. Employing simulated annealing, we reveal the stabilization of three distinct double-Q phases in the absence of an external magnetic field, each characterized by noncoplanar spin textures with spatially modulated local scalar spin chirality. Under applied magnetic fields, we identify field-induced phase transitions among single-Q, double-Q, and triple-Q states, some of which exhibit a finite net scalar spin chirality indicative of topologically nontrivial order. These findings highlight centrosymmetric systems with sublattice-dependent Dzyaloshinskii–Moriya interactions as promising platforms for realizing a variety of multiple-Q spin textures. Full article

The origin of homochirality by rotational magnetoelectrochemistry was theoretically examined. Electrochemical reductions in a rotating solution under a static vertical magnetic field were concluded to yield microscopic vortices with L-activity for enantiomeric reagents, whereas D-active vortices arise from electrochemical oxidation. The reduction case was experimentally verified by rotational magnetoelectrodeposition (RMED) of copper films using an electrolysis cell rotating in a magnetic field, where L-active screw dislocations were created by L-active microscopic vortices. In all the cases of the directions of magnetic polarity and system rotation, the RMED films exhibited L-activity for the enantiomeric reactions of amino acids. Full article

Intense circularly polarized luminescence is crucial for high-performance electroluminescent, optoelectronic, and photonic devices. This study investigates the magneto-chiral characteristics of two achiral soluble diamagnetic perovskite-type PbQDs. Magnetic fields of 158 and 198 mT are applied using an electromagnet in a toluene solution at 25 °C. Both PbQDs show a magnetic circularly polarized luminescence magnitude of approximately 10⁻³ within the (480 to 580) nm wavelength range. The strength of the magnetic circularly polarized luminescence increases with the intensity of the applied magnetic field. Furthermore, the study demonstrates rapid and reversible switching of the rotation direction of the magnetic circularly polarized luminescence when the magnetic poles are rapidly changed. These results suggest that the direction (right- and left-rotating light) and circular polarization of circularly polarized luminescence (CPL) from circularly polarized perovskites can be alternately and freely controlled by applying an external magnetic field with an appropriate direction and strength. Full article

The enzyme ω-transaminase (ω-TA) has garnered significant attention due to its capacity to catalyze the synthesis of chiral amines with high efficiency. Nevertheless, the lack of stability of ω-TA and the difficulty of recycling and reuse are still challenges that limit its application. This study developed a novel magnetic nanocellulose composite carrier (NNC@Fe₃O₄@Ni), synthesized from microcrystalline cellulose via low-eutectic solvent treatment, amine modification, and metal hybridization. The NNC@Fe₃O₄@Ni was characterized by FTIR, XPS, XRD, BET, and VSM. Additionally, the performance and catalytic behavior of the immobilized enzyme were investigated. The results revealed that NNC@Fe₃O₄@Ni exhibited a high specific surface area, superparamagnetism, and dual-site functionality (amine/Ni²⁺). Response Surface Methodology (RSM) optimized the carrier-enzyme interaction parameters, yielding optimal immobilization conditions: a mass ratio of 50.8 mg g⁻¹, temperature of 12.5 °C, and duration of 58.6 min, achieving 82.91% enzyme activity recovery. Compared to free enzymes, the immobilized variant demonstrated enhanced catalytic stability, with expanded optimal pH (9.0) and temperature (30 °C). Thermal stability assessments showed 84.39% activity retention after 5 h at 30 °C and 90.30% residual activity post-120 h storage. The catalyst maintained >80% efficiency over 10 reuse cycles. These findings confirm the efficacy of magnetic nanocellulose carriers in enhancing ω-TA stability, reusability, and catalytic performance, offering a viable strategy for industrial biocatalytic processes. Full article

Recently, significant effort has been devoted to enhancing magnetic anisotropy energy (MAE) and the Dzyaloshinskii–Moriya interaction (DMI) in two-dimensional (2D) ferromagnetic materials through various tuning approaches. Among these methods, defect engineering is one of the most effective strategies. However, the influence of these charged defects on the MAE and DMI is unclear. Therefore, we systematically investigate the defect effect on the MAE and DMI of I vacancy-doped (v_I-CrI₃), 3d-transition-metal-doped (TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) (3d-TM_i@CrI₃), and v_I-TM co-doped (3d-TM_i@v_I-CrI₃) monolayer CrI₃ using first-principles calculations. Our results indicate that Cr-rich conditions can promote the defect formation of v_I-CrI₃, 3d-TM_i@CrI₃, and 3d-TM_i@v_I-CrI₃ systems and demonstrate that 49 types of charged systems are stable. Among these systems, the Cu_i@v_I-CrI₃ in the +1 charge state (Cu_i^•@v_I-CrI₃) system has a smaller defect formation energy, exhibiting a large MAE exceeding 30 meV, and the ratio (D/J) of the antisymmetric magnetic exchange parameter (D) to the Heisenberg exchange parameter (J) reaches 1.04. The large MAE originates from the transition from single-ion anisotropy (SIA) to covalent interaction anisotropy (CIA) due to the coupling variation between the p_y and p_x orbitals of I atoms near the Fermi level caused by charge states. The enhancement of the DMI is due to the electrostatic potential differences between the I-top and I-bottom layers, which are conducive to forming stable chiral spin textures. This study provides insight into the defect charge state modulating the magnetism of 2D magnetic materials. Full article

A mononuclear complex [Dy(phenN₆)(HL′)₂]PF₆·CH₂Cl₂ (H₂L′ = R/S-1,1′-binaphthyl-2,2′-diphenol) with local D_6h symmetry was synthesized. Structural determination shows that Dy³⁺ was encapsulated within the coordination cavity of the neutral hexaaza macrocyclic ligand phenN₆, forming a non-planar coordination environment. The axial positions are occupied by two phenoxy groups of binaphthol in the trans form. The local geometry of Dy³⁺ closely resembles a regular hexagonal bipyramid D_6h configuration. The axial Dy-O_phenoxy distances are 2.189(5) and 2.145(5) Å, respectively, while the Dy-N bond lengths in the equatorial plane are in the range of 2.524(7)–2.717(5) Å. The axial O_phthalmoxy-Dy-O_phthalmoxy bond angle is 162.91(17)°, which deviates from the ideal linearity. Under the excitation at 320 nm, the complex exhibits a characteristic emission peak at 360 nm, corresponding to the naphthalene ring. The AC susceptibility measurements under an applied DC field of 1800 Oe show distinct temperature-dependent and frequency-dependent AC magnetic susceptibility, typical of single-molecule magnetic behavior. The Cole–Cole plot in the temperature range of 6.0–28.0 K was fitted using a model incorporating Orbach and Raman relaxation mechanisms, giving an effective energy barrier of U_eff = 300.2 K. Theoretical calculations on complex 1 reveal that the magnetization relaxation proceeds through the first excited Kramers doublets with a calculated magnetization blocking barrier of 404.1 cm⁻¹ (581.4 K). Full article

By chiral effects, one understands the manifestations of chiral gauge anomaly and of gravitational chiral anomaly in hydrodynamics. In the last two to three years, our understanding of chiral effects has considerably changed. Here, we present a mini-review of two topics: first, a shift in understanding symmetry, which underlies the chiral magnetic effect and second, the interpretation of the chiral kinematical effect uncovered recently. Full article

We demonstrate tunable ferrimagnetic properties in both bulk and thin film ferrimagnetic DyCo₃ compatible with the hosting of topological magnetic chiral textures, namely skyrmions suitable for integration into spintronic applications with classic, neuromorphic and quantum functionalities. The bulk samples were prepared by arc-melting of stoichiometric mixtures under purified argon atmosphere and the thin films by Ultra-High-Vacuum magnetron sputtering from a stoichiometric target. Magnetometry allows us to extract the main magnetic properties of bulk and thin films: the saturation magnetization, the magnetic anisotropy and their variation with temperature. These results are successfully complemented by band structure ab initio DFT calculations. Based on the critical magnetic parameters extracted from experiments, we performed micromagnetic simulations that reveal the skyrmionic potential of our samples in both continuous thin film and nano-patterned architectures. Full article

This study reports the synthesis of novel multilayer 3D chiral polymers using 2,2′-(2,7-Naphthalenediyl)bis[4,4,5,5-tetramethyl-1,3,2-dioxaborolane] and 1,8-dibronaphthalene along with its derivatives as key precursors. Comprehensive characterization was performed using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), photoluminescence, ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), polarimetry, dynamic light scattering (DLS), and thermogravimetric analysis (TGA). Notably, the polymers exhibited remarkable aggregation-induced emission (AIE) and aggregation-induced polarization (AIP) phenomena, revealing enhanced luminescence and optical activity in aggregated states. These findings underscore the potential of these chiral polymers for applications in optoelectronics and advanced sensing technologies, highlighting the intricate relationship between molecular structure and optical behavior. Full article

Recent experiments have reported distinct handedness of spin waves across the compensation temperatures of ferrimagnets, offering promising functionalities for ferrimagnet-based magnonic applications with two distinct polarizations. This paper investigates the effects of various factors on the compensation points of GdFe ferrimagnets through atomistic-level spin dynamics simulations. The results show that as the Gd composition increases, both the magnetization compensation temperature and the angular momentum compensation temperature of the GdFe alloy increase, with a linear relationship observed between the two compensation temperatures. Furthermore, we show that external magnetic fields and antiferromagnetic exchange strength can also modulate the compensation temperatures. Moreover, the antiferromagnetic exchange strength also affects the resonance frequency of ferrimagnetic materials. In the absence of an external field, the resonance frequency of GdFe is divided into two branches and both increase linearly with the increase in antiferromagnetic exchange strength. This study may stimulate fundamental research on compensated ferrimagnets, which may be useful for building chirality-based spintronics. Full article

Hexagonal BCN (h-BCN), an isoelectronic counterpart to graphene, exhibits chirality and offers the distinct advantage of optical activity in the vacuum ultraviolet (VUV) region, characterized by significantly higher wavelengths compared to graphene nanoflakes. h-BCN possesses a wide bandgap and demonstrates desirable semiconducting properties. In this study, we employ Density Functional Theory (DFT) calculations to investigate the proximity effects of adsorbed h-BCN flakes on two-dimensional (2D) substrates. The chosen substrates encompass monolayers of 3D transition metals and WSe₂, as well as a bilayer consisting of WSe₂/Ni. Notably, the hydrogen-terminated h-BCN nanoflakes retain their planar configuration following adsorption. We observe a strong interaction between h-BCN and fcc-based monolayers such as Ni(111), resulting in the closure of the optical bandgap, while the adsorption energy on WSe₂ is significantly weaker, preserving an approximate 1.1 eV bandgap. Furthermore, we demonstrate the magnetism induced by the proximity of adsorbed chiral h-BCN molecules, and the chiral-induced spin selectivity within the proposed systems. Full article

This study explores Hall transport phenomena by expanding upon prior research on magnetic disk arrays (MDAs). We examine the dynamics of charged particles using collision models akin to those in Lorentzian plasma. Previously, we derived transport coefficients under isotropic and mono-kinetic conditions. In this study, we adopt an anisotropic framework, enhanced by Fourier transformation, and employ the local Maxwellian distribution function. These assumptions allow us to calculate the Hall diffusivity, electrical conductivity, and thermal Hall conductivity tensors. Our findings contribute to a deeper understanding of the Hall transport in magnetic disk arrays and chiral active systems. Full article

Well-defined amorphous/semi-crystalline statistical copolymers of n-dodecyl isocyanate, DDIC, and allyl isocyanate, ALIC, were synthesized via coordination polymerization using the chiral half-titanocene complex CpTiCl₂(O-(S)-2-Bu) as an initiator. In the frame of the terminal model, the monomer reactivity ratios of the statistical copolymers were calculated using both well-known linear graphical methods and the computer program COPOINT. The molecular and structural characteristics of the copolymers were also calculated. The thermal properties of these samples were studied by differential scanning calorimetry, DSC, measurements. The kinetics of the thermal decomposition of the statistical copolymers was studied by thermogravimetric analysis, TGA, and differential thermogravimetry, DTG, and the activation energy of this process was calculated by employing several theoretical models. Moreover, block copolymers with the structure P[DDIC-b-(DDIC-co-ALIC)] were synthesized by sequential addition of monomers and coordination polymerization methodologies. The samples were characterized by nuclear magnetic resonance, NMR, spectroscopy; size exclusion chromatography, SEC; and DSC. The thermal stability of the blocks was also studied by TGA and DTG and compared to the corresponding statistical copolymers, showing that the macromolecular architecture greatly affects the properties of the copolymers. A thiol-ene click post-polymerization reaction was performed to introduce aromatic groups along the polyisocyanate chain in order to improve the thermal stability of the parent polymers. Evidently, these statistical and block copolymers can be employed as precursors for the synthesis of novel polyisocyanate-based materials. Full article