Magnetic Properties Research Articles

Magnetic Properties, Spin-Vibration Couplings, and Temperature Effects in Phenalenyl and Triangulene.

We introduce a computational methodology for evaluating and analyzing spin-vibration couplings in molecular systems, enabling insights into the interplay between electronic spins and molecular vibrations. By mapping ab initio electronic structure calculations onto molecular spin Hamiltonians, our approach captures those vibrational interactions potentially driving spin relaxation process. Spin-vibration couplings, derived from Holstein and Peierls terms, highlight the pivotal role of vibrational mode symmetry in spin decoherence and efficient energy dissipation. Additionally, second-order couplings provide a framework to explore the temperature dependence of spin properties via the thermal population of higher vibrational levels. Applied to phenalenyl and [3]triangulene, the results indicate that direct spin transitions dominate over Orbach relaxation in both systems. Hyperfine interactions primarily dictate spin-vibration couplings and thermal effects in phenalenyl, whereas zero-field splitting contributions are dominant in [3]triangulene. These findings advance the understanding of spin relaxation mechanisms in organic molecular systems.

Ferrites with a Minimized Secondary Electron Yield.

Ferrites are an essential material in modern industry due to their exceptional magnetic properties and high resistivity. Many applications of ferrites necessitate exposure to high energy electrons, particularly space science and particle accelerators, where charging, multipacting, and electron clouds (ECs) are major issues. ECs are of particular concern around the Ni/Zn soft ferrite kicker magnets as the large hadron collider (LHC) undergoes its high luminosity upgrade. Here, laser engineered surface structures (LESS) are used to reduce the secondary electron yield (SEY) of Ni/Zn ferrites from 2.1 to its experimentally determined minimum of 0.81, eliminating the ferrites ability to contribute to the formation of ECs. This demonstrates the applicability of LESS outside of metals and its broader applicability to reducing the SEY of technical materials.

Design of organic crystals with lone pairs to study spin resonance and spin-lattice interactions

Lone pairs are widely prevalent in various types of molecules and have a significant impact on the band structure, carrier transport, and dielectric response, which are the key factors for exploring the underlying mechanism of phenomena in opto-spintronics. In this work, nitrogen substitutions with nonequivalent hybridization are adopted to obtain different types of organic charge transfer crystals, where lone pairs are generated to weaken the interactions between donors and acceptors, resulting in a blueshift in photoluminescence and a weaker electron-lattice coupling. Moreover, lone pairs could further strengthen the ability to transfer energy and spin angular momentum to the lattice vibration to enhance spin resonance. Additionally, due to the effect of lone pairs, the spin density inside the crystals is redistributed to tune the transition between the singlet and triplet states. Overall, crystals with lone pairs demonstrate a more diverse set of magnetic, optical, and spin-related properties.

Investigating magnetic and optical properties of layered iron phosphorus trisulfide intercalated with organic compounds

Investigating magnetic and optical properties of layered iron phosphorus trisulfide intercalated with organic compounds

Unveiling the Werner-Type Cluster Chemistry of Heterometallic 4f/Post-Transition Metals: A {Dy3Bi8} Complex Exhibiting Quantum Tunneling Steps in the Hysteresis Loops and its 1-D Congener.

A new [Dy3Bi8O6Cl3(saph)9] (1) Werner-type cluster has been prepared, which is the first DyIII/BiIII polynuclear compound with no metal-metal bond and one of the very few LnIII-BiIII (Ln = lanthanide) heterometallic complexes reported to date. The molecular compound 1 has been deliberately transformed to its 1-D analogue [Dy3Bi8O6(N3)3(saph)9]n (2) via the replacement of the terminal Cl- ions by end-to-end bridging N3- groups. The overall metallic skeleton of 1 (and 2) can be described as consisting of a diamagnetic {Bi8} unit with an elongated trigonal bipyramidal topology, surrounded by a magnetic {Dy3} equilateral triangle, which does not contain μ3-oxo/hydroxo/alkoxo groups. Detailed magnetic studies in a microcrystalline sample and a single crystal of 1 revealed a rare two-step hysteresis loop at various low temperatures and field-sweep rates, with the steps located at zero and ±0.26 T fields providing a measure of intermolecular interactions. Extended ab initio calculations unravel the dominant pathways of magnetization relaxation, as well as the type and magnitude of the magnetic exchange interactions between the DyIII centers and the orientation of their anisotropy axes, thus rendering the {Dy3} unit of 1 as a rare triangle among its congeners with a nontoroidal magnetic state. The combined results demonstrate the potential of heterometallic lanthanide/post-transition metal chemistry to provide molecule-based materials with unprecedented structures and compelling methods to rationalize the obtained magnetic properties.

Inhibitory effect of magnetic aqueous extract of Syzygium aromaticum L on two types of oral pathogenic bacteria

<p><strong>Aim</strong> Magnetic fields affect all living things, which is why they are the subject of extensive research around the world. The aim of this study was to investigate the effects of different levels of static magnetic field on chemical behaviours of aqueous extract of <em>Syzygium aromaticum</em> L and their effect on selective oral pathogenic bacteria. <br /><strong>Methods</strong> This study utilized locally manufactured dipolar static magnetic fields with strengths between 1200 and 3200 Gauss, measured by a Sylocimol Residence magnetizer. Gram positive G (+) <em>Streptococcus viridans</em> and G negative (G-) <em>Porphyromonas gingivalis</em> strains were used in studies on the antimicrobial properties of <em>S. aromaticum</em> extract. Tests were carried out using the clove essential component (eugenol) and its functionalized extract to evaluate various bacterial inhibitions and establish whether there is a synergistic effect between the extract and subjected to the magnetic field. <br /><strong>Results</strong> Polyphenol extraction increased with eugenol content. The analytical method's reliability was confirmed by chromatograms of eugenol and eugenol acetate standards, demonstrating good separation of compounds. The selectivity of the method was guaranteed by the purity index of the eugenol and eugenol acetate peaks. The aqueous extract of <em>S. aromaticum</em> showed magnetic properties. The extract showed antimicrobial activity against two bacterial strains. Cell viability changed at different magnetic field intensities, and the inhibition zone for <em>P. gingivalis</em> increased significantly due to prolonged exposure.  <br /><strong>Conclusion</strong> The magnetized extract inhibits both G (+) and G (-) bacteria when combined with clove extract.</p>

Electrosynthesis of Silane-Modified Magnetic Nanoparticles for Efficient Lead Ion Removal.

The removal of heavy metal ions, such as lead (Pb2+), from aqueous systems is critical due to their high toxicity and bioaccumulation in living organisms. This study presents a straightforward approach for the synthesis and surface modification of iron oxide nanoparticles (IONPs) for the magnetic removal of Pb2+ ions. IONPs were produced via electrosynthesis at varying voltages (10-40 V), with optimal magnetic properties achieved at 40 V resulting in highly crystalline and magnetic IONPs in the gamma-maghemite (γ-Fe2O3) phase. IONPs were characterized using various techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). A novel electrochemical method was developed for the silanization of IONPs using tetraethoxysilane (TEOS), (3-mercaptopropyl)trimethoxysilane (MPTMS) and (3-aminopropyl)triethoxysilane (APTES). The resulting silane-modified IONPs were evaluated for the magnetic removal of Pb2+ ions, with TEOS-modified IONPs demonstrating superior performance. This material exhibited a high adsorption capacity of 519 mg/g at a Pb2+ ion concentration of 300 ppm, and high removal efficiency across a range of Pb2+ ion concentrations, attributed to its Fe2O3@SiO2 core-shell structure. This study highlights the potential of the electrochemical synthesis and silanization of nanoparticles for heavy metal remediation in water.

Recent Advances of Colossal Magnetoresistance in Versatile La-Ca-Mn-O Material-Based Films

Hole-doped manganese oxides exhibit a gigantic negative magnetoresistance, referred to as colossal magnetoresistance (CMR), owing to the interplay between double-exchange (DE) ferromagnetic metal and charge-ordered antiferromagnetic insulator/semiconductor phases. Magnetoresistive manganites display a sharp resistivity drop at the metal–insulator transition temperature (TMI). CMR effects in perovskite manganites, specifically La0.67Ca0.33MnO3 (La-Ca-Mn-O or LCMO), have been extensively investigated. This review paper provides a comprehensive introduction to the crystallographic structure, as well as the electronic and magnetic properties, of LCMO films. Furthermore, we delve into a detailed discussion of the effects of epitaxial strain induced by different substrates on LCMO films. Additionally, we review the early findings and diverse applications of LCMO thin films. Finally, we outline potential challenges and prospects for achieving superior LCMO film properties.

A generative model for inorganic materials design.

The design of functional materials with desired properties is essential in driving technological advances in areas like energy storage, catalysis, and carbon capture1-3. Generative models provide a new paradigm for materials design by directly generating novel materials given desired property constraints, but current methods have low success rate in proposing stable crystals or can only satisfy a limited set of property constraints 4-11. Here, we present MatterGen, a model that generates stable, diverse inorganic materials across the periodic table and can further be fine-tuned to steer the generation towards a broad range of property constraints. Compared to prior generative models 4,12, structures produced by MatterGen are more than twice as likely to be novel and stable, and more than 10 times closer to the local energy minimum. After fine-tuning, MatterGen successfully generates stable, novel materials with desired chemistry, symmetry, as well as mechanical, electronic and magnetic properties. As a proof of concept, we synthesize one of the generated structures and measure its property value to be within 20 % of our target. We believe that the quality of generated materials and the breadth of MatterGen's capabilities represent a major advancement towards creating a foundational generative model for materials design.

Microstructure and Thermal Cyclic Behavior of FeNiCoAlTaB High-Entropy Alloy

This study investigates the grain morphology, microstructure, magnetic properties and shape memory properties of an Fe41.265Ni28.2Co17Al11Ta2.5B0.04 (at%) high-entropy alloy (HEA) cold-rolled to 98%. The EBSD results show that the texture intensities of the samples annealed at 1300 °C for 0.5 or 1 h are 2.45 and 2.82, respectively. This indicates that both samples were formed without any strong texture. The grain morphology results show that the grain size increased from 356.8 to 504.6 μm when the annealing time was increased from 0.5 to 1 h. The large grain size improved the recoverable strain due to a reduction in the grain constraint. As a result, annealing was carried out at 1300 °C/1 h for the remainder of the study. The hardness decreased at 24 h, then increased again at 48 h; this phenomenon was related to the austenite finish temperature. Thermo-magnetic analysis revealed that the austenite finish temperature increased when the samples were aged at 600 °C for between 12 and 24 h. When the aging time was prolonged to 48 h, the austenite finish temperature value decreased. X-ray diffraction (XRD) demonstrated that the peak of the precipitates emerged and intensified when the aging time was increased from 12 to 24 h at 600 °C. From the three-point bending shape memory test, the samples aged at 600 °C for 12 and 24 h had maximum recoverable strains of 2% and 3.6%, respectively. The stress–temperature slopes of the austenite finish temperature were 10.3 MPa/°C for 12 h and 6 MPa/°C for 24 h, respectively. Higher slope values correspond to lower recoverable strains.

The Multiple Effects of RE Element Addition in Non-Oriented Silicon Steel

High-grade non-oriented silicon steel with high magnetic induction and low iron loss produced with low carbon emissions is crucial for the development of new energy and energy-saving motors. In this paper, the trace mixed rare earth (RE) elements exhibit a great potential to enhance magnetic properties in a lower carbon emission process by multiple effects on microstructure, texture, and inclusion in non-oriented silicon steel. With the trace-doped RE elements (0.004–0.030%), RE-rich precipitates preferentially form and subsequently adsorb fine inclusions below 1 μm to transform into spherical or ellipsoidal shape, which results in a significant increase in final recrystallization grain size. Moreover, the favorable λ texture (<001>//ND) is promoted while the detrimental γ texture (<111>//ND) is reduced, owing to the advantages in size and quantity of λ grains during the nucleation process. The improved magnetic properties of higher B50 and lower P15/50 are achieved with 0.004% RE at lower annealing temperature ranges. The increased λ texture is attributed to the heterogeneity in microstructure and texture as well as the grain boundary segregation of RE elements. However, a higher RE content (0.072%) leads to a deterioration in magnetic performance due to the formation of more stable RE-rich precipitates, smaller grains, and stronger γ texture. An iron loss calculation model was also proposed to guide the design of high-grade non-oriented silicon steel by incorporating the multiple effects of RE elements on grain size, recrystallization texture, and inclusion.

First-Principles Insights into the Structural, Electronic, Magnetic, Mechanical, Thermoelectric, and Thermodynamic Properties of Filled Skutterudites CePt4X12 (X = As, Sb)

First-Principles Insights into the Structural, Electronic, Magnetic, Mechanical, Thermoelectric, and Thermodynamic Properties of Filled Skutterudites CePt4X12 (X = As, Sb)

Lanthanide-Germanate Adelite, LnCo(GeO4)(OH) (Ln = La-Sm), with Edge-Sharing Octahedral Chains of Co2+ Ions: Spin Frustration Expected to Form Cycloids.

A new series of P212121 adelite-type LnCo(GeO4)(OH) (Ln = La-Sm) single crystals were grown by a high-temperature, high-pressure hydrothermal method (650 °C and 100 MPa). Single-crystal diffraction refinements yielded chiral one-dimensional (1D) chains of Co2+ along the a axis with an average 2.98 Å separation between Co2+ centers in the [CoO2(OH)2]∞ ribbon chains. A three-dimensional (3D) superstructure is formed by a bridging lanthanide-germanium framework formed by two unique alternating 5.83 and 6.00 Å distances between interchain Co2+ centers along the a axis. Magnetic studies of the S = 3/2 Co2+ chains in LaCo(GeO4)(OH) revealed a highly anisotropic structure with a common Néel temperature of 32 K. Additionally, a spin-flip transition occurs at 2 K when a 7.3 T field is applied along the chain. Zero-field cooled susceptibility at this critical field resulted in a complex intermediate state consisting of three unique antiferromagnetic transitions at 3, 8, and 16 K. The spin exchanges of LaCo(GeO4)(OH) evaluated by density functional theory calculations show the presence of spin frustration in the 1D chains, which can lead to a cycloidal magnetic structure within the plane of [CoO2(OH)2]∞ chains. The observed magnetic properties are explained by considering the competition between the 1D intrachain and 3D-1D interchain antiferromagnetic interactions.

Biomagnetic monitoring of urban atmospheric pollution: A review of magnetic signatures from different types of plants.

Biomagnetic monitoring has rapidly emerged as a valuable tool in urban atmospheric pollution (UAP) assessment due to its high spatial resolution, complementing traditional monitoring systems. This review systematically elucidates the principles of plant dust retention and the factors influencing it, while also reviewing the advancements in global research on UAP monitoring through the magnetic properties of various plant species. We provide a comprehensive analysis of the current applications of biomagnetic monitoring in UAP and identify critical challenges, including species-specific monitoring discrepancies, complex pollution sources, and non-standardized sample preparation methods. Additionally, we propose future research directions to address these challenges and enhance the efficacy of biomagnetic monitoring in UAP.

Magnetic order and long-range interactions in mesoscopic Ising chains

We investigate the design of magnetic ordering in one-dimensional mesoscopic magnetic Ising chains by modulating long-range interactions. These interactions are affected by geometrical modifications to the chain, which adjust the energy hierarchy and the resulting magnetic ground states. Consequently, the magnetic ordering can be tuned between antiferromagnetic and antiferromagnetic dimer phases. These phases are experimentally observed in chains fabricated using both conventional electron-beam lithography and ion implantation techniques, demonstrating the feasibility of controlling magnetic properties at the mesoscale. The ability of attaining these magnetic structures by thermal annealing, underlines the potential of using such systems instead of simulated annealers in tackling combinatorial optimization tasks. Published by the American Physical Society 2025

4D Printing of Magnetic Shape Memory Polymer—La0.7Sr0.3MnO3 Nanocomposite

Four‐dimensional printing has revolutionized traditional three‐dimensional printing (3D printing) by using smart materials such as shape memory polymers (SMPs). As nonmagnetic materials, SMPs require direct exposure to heat for the shape memory effect to be triggered. This limitation can be addressed by incorporating magnetic nanoparticles, allowing the SMP/nanocomposite to be remotely heated through induction heating. This work focuses on the (LSMO) manganite with an optimized stoichiometry of x = 0.3. Polycrystalline LSMO is sintered from pure powders and later added to SMP through the solution mixing route, and finally extruded into filaments to be used for 3D printing. Significant improvements in the elastic modulus, yield, and ultimate strengths are observed following LSMO addition. All the composites exhibit magnetic moments near 3.5 μB Mn−1 at the ground state indicating desirable magnetic properties. Shape memory properties are evaluated following the application of programming and recovery cycles on the as‐printed single‐cell auxetic structure. The evaluation of the bulk strain on the auxetic structure for 0 and 20 wt% LSMO/SMP nanocomposite reveals no change in shape fixity, a slight decrease in shape recovery ratio from 88 to 81%, and a significant improvement in the shape recovery rate from 124.3 to 179.5% min−1.

Exploring Brannerite-Type Mg1−xMxV2O6 (M = Mn, Cu, Co, or Ni) Oxides: Crystal Structure and Optical Properties

Environmentally benign, highly stable oxides exhibiting desirable optical properties and high near-IR reflectance are being researched for their potential application as pigments. Mg1−xMxV2O6 (M = Mn, Cu, Co, or Ni) oxides with brannerite-type structures were synthesized by the conventional solid-state reaction method to study their optical properties. These series exhibit structural transitions from brannerite (C2/m) to distorted brannerite (P1¯) and NiV2O6-type (P1¯) structures. The average color of Mg1−xMxV2O6 compounds varies from reddish-yellow to brown to dark brown. The L*a*b* color coordinates reveal that Mg1−xCuxV2O6 and Mg1−xNixV2O6 show more red hues in color with x = 0.4 and x = 0.5, respectively. The UV–Vis diffuse reflectance spectra indicate a possible origin for these results include the ligand-to-metal charge transfer (O2− 2p-V5+ 3d), metal-to-metal charge transfer (from Mn2+ 3d/Cu2+ 3d/Co2+ 3d/Ni2+ 3d to V5+ 3d), band gap transitions, and d–d transitions. Magnetic property measurements revealed antiferromagnetic behavior for the compounds Mg1−xMxV2O6 (M = Mn, Cu, Co, and Ni), and an oxidation state of +2 for the M ions was deduced from their Curie–Weiss behavior. The system Mg1−xMnxV2O6 has a NIR reflectance in the range between 40% and 70%, indicating its potential to be utilized in the pigment industry.

Deconstructing the Properties of Solar Super Active Region 13664 in the Context of the Historic Geomagnetic Storm of 2024 May 10–11

Abstract Active regions (ARs) are sites of strong magnetic fields on the solar surface whose size can be several times that of Earth. They spawn dynamic activity, sometimes resulting in severe space weather. Some ARs characterized by extraordinary magnetic properties and exhibiting extreme activity are termed as super active regions (SARs). Recently, solar AR 13664 produced 23 X-class flares and unleashed multiple coronal mass ejections, which triggered a severe geomagnetic storm during 2024 May 10–11—the strongest storm on record since 2003. Here, we put AR 13664 in historical context over the cumulative period of 1874 May–2024 June. We find that AR 13664 stands at the 99.95th percentile in the distribution of area over 1874 May–2024 June and at the 99.10th percentile in terms of flux content among all ARs over the period 1996 April–2024 June. Our analysis indicates that five of its magnetic properties rank at the 100.00th percentile among all ARs observed during 2010 May–2024 June by the Solar Dynamic Observatory. A total of 16 magnetic properties of AR 13664 are ranked higher than the 99.00th percentile when compared to other ARs recorded in Space-weather Helioseismic Magnetic Imager Active Region Patch data series, which includes all well-established flare relevant parameters. Furthermore, we demonstrate that AR 13664 reached its most dynamic flare productive state following a rapid rate of rise of its flare-relevant parameters and that the X-class flares were more frequent near their peak values. Our analyses establish AR 13644 to be an SAR and provide a paradigm for investigating their flare-relevant physical characteristics.

Proton-Induced Switching of Paramagnetism: Reversible Conversion between a Low and High Spin CoIII Center within a Heterobimetallic Core.

The development of molecular species with switchable magnetic properties has been a long-standing challenge in chemistry. One approach involves binding an analyte, such as protons, to a compound to trigger a change in magnetism. Transition metal complexes have been targeted for this type of magnetic modulation because they can undergo changes in their spin states. However, heterobimetallic complexes have had limited utility because of a lack of ligands that create differentiated structures around each metal center that are often necessary to regulate the electronic and magnetic properties. To circumvent this problem, we have used a tripodal ligand with phosphinic amido groups to prepare a complex with a discrete [CoIII(μ-OH)FeIII] core and an overall system spin of ST = 5/2. Deprotonation readily produces a species with a unique [CoIII(μ-O)FeIII] core and an ST = 1/2 system spin. X-ray diffraction studies, electron paramagnetic resonance spectroscopy, and Mössbauer spectroscopy pinpoint the hexacoordinate CoIII center as the cause of this spin change: the typical SCo = 0 spin state of the CoIII center in the [CoIII(μ-OH)FeIII] complex switches to a rare SCo = 2 spin state in the [CoIII(μ-O)FeIII] analogue; this change turns on antiferromagnetic coupling between the two metal centers. Computational studies link an increase in π bonding within the Co-oxido unit to the change in the CoIII spin state. The conversion is reversible and provides a blueprint for using oxido/hydroxido ligands within a heterobimetallic core to regulate the spin state of a metal site and thus modulate the paramagnetism of a system.

Ferroelectricity with concomitant Coulomb screening in van der Waals heterostructures.

Interfacial ferroelectricity emerges in non-centrosymmetric heterostructures consisting of non-polar van der Waals (vdW) layers. Ferroelectricity with concomitant Coulomb screening can switch topological currents or superconductivity and simulate synaptic response. So far, it has only been realized in bilayer graphene moiré superlattices, posing stringent requirements to constituent materials and twist angles. Here we report ferroelectricity with concomitant Coulomb screening in different vdW heterostructures free of moiré interfaces containing monolayer graphene, boron nitride (BN) and transition metal chalcogenide layers. We observe a ferroelectric hysteretic response in a BN/monolayer graphene/BN, as well as in BN/WSe2/monolayer graphene/WSe2/BN heterostructure, but also when replacing the stacking fault-containing BN with multilayer twisted MoS2, a prototypical sliding ferroelectric. Our control experiments exclude alternative mechanisms, such that we conclude that ferroelectricity originates from stacking faults in the BN flakes. Hysteretic switching occurs when a conductive ferroelectric screens the gating field electrically and controls the monolayer graphene through its polarization field. Our results relax some of the material and design constraints for device applications based on sliding ferroelectricity and should enable memory device or the combination with diverse vdW materials with superconducting, topological or magnetic properties.