Magnetite (Fe3O4) nanoparticles (NPs) were obtained through polyol synthesis followed by a particle-growth treatment at 260 °C, without external surfactants, to evaluate the method's efficiency for producing magnetic nanoparticles with a well-defined crystalline structure, colloidal stability, and surface functionalization. The NPs were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermal analyses, dynamic light scattering, transmission electron microscopy, Mössbauer spectroscopy, and magnetometry. X-ray diffraction confirmed predominant magnetite formation, with a cubic spinel-type structure and an average crystallite size of approximately 16.75 nm. The FTIR and TG/DSC analyses indicated the presence of organic groups derived from Terathane on the nanoparticles' surface, highlighting the polyol's role as a stabilizing agent. No visible sedimentation or macroscopic aggregation was observed in ethanol, THF, or chloroform after 45 days. DLS analysis indicated an average hydrodynamic diameter of 31 nm, while TEM images revealed nearly spherical particles with an average diameter of approximately 10.41 nm. Mössbauer spectroscopy confirmed the predominance of magnetite and indicated magnetic relaxation effects, while magnetometry revealed a magnetically soft response, with a saturation magnetization of 54.91 emu·g−1, a coercive field of 0.188 kOe, and a remanent magnetization of 12.63 emu·g−1. Thus, the proposed route proved to be simple and efficient for synthesizing Fe3O4 nanoparticles with promising properties for applications in magnetic colloids, nanocomposites, environmental remediation, and biomedical technologies.
The Lieb lattice, featuring the coexistence of Dirac-like dispersions and a perfectly flat band, constitutes a paradigmatic platform for investigating the interplay between band topology, many-body interactions, and external perturbations. In this work, we present a comprehensive theoretical study of the combined effects of Holstein electron–phonon coupling and a perpendicular magnetic field on the dynamical and static charge structure factors of a doped Lieb lattice. Employing a full-band Green’s function formalism combined with the random-phase approximation, we derive the phonon-mediated effective electron–electron interaction and compute the charge susceptibilities. Our results reveal that the frequency, intensity, and spectral weight of plasmon peaks in the dynamical charge structure factor can be systematically tuned. The controlling parameters are the electron–phonon coupling strength, Zeeman field, next-nearest-neighbor hopping, staggered on-site potential, and carrier doping. In particular, increasing the Holstein coupling induces a pronounced blueshift of the high-frequency plasmon mode. This blueshift is accompanied by a non-monotonic variation of the mode intensity. In contrast, the perpendicular magnetic field produces a redshift and a suppression of the plasmon resonance. The static charge structure factor exhibits rich non-monotonic dependencies on magnetic field and hopping amplitude. These dependencies reflect the competition between thermal fluctuations, spin polarization, and polaronic effects. These findings establish a unified framework for the control of collective charge excitations and charge correlations via Holstein electron–phonon coupling and perpendicular magnetic fields. The resulting tunability of plasmon frequencies, spectral weights, and static charge correlations offers concrete design principles for reconfigurable plasmonic responses and engineered charge correlations in artificial quantum lattices and photonic platforms.
Bimetallic nanowires (NWs) integrating magnetic, electrical, and catalytic functionalities are of interest for multifunctional nanostructured systems. Herein, Ag@Ni core-shell NWs were synthesized through a two-step route using preformed Ag NWs as the core and a Ni-containing shell. SEM, TEM, EDS elemental mapping, line-scan analysis, and XRD collectively supported the formation of an Ag-rich core surrounded by a spike-decorated polycrystalline Ni-containing shell. Magnetic hysteresis measurements revealed ferromagnetic behavior at 300 and 10 K, with coercivities of approximately 53 and 80 Oe, respectively. ZFC/FC measurements under 100 Oe showed thermomagnetic irreversibility, with the two curves becoming nearly coincident near the upper end of the measured temperature range of 340–350 K. Representative individual-NW devices exhibited approximately linear I-V characteristics under zero magnetic field, and the effective resistivity of the Ag@Ni NWs was 4.4×10−4Ω⋅cm, intermediate between those of Ag and Ni NWs. In NaBH4 hydrolysis, the Ag@Ni NWs showed the fastest overall hydrogen-evolution profile among the tested samples under identical total-catalyst-mass conditions. These results show that the prepared Ag@Ni core-shell NWs exhibit ferromagnetic behavior, electrical conduction, and catalytic hydrogen-generation activity under the respective measurement conditions.
As early as in 1988, the IEC discussed the application of tangential field coil (H-coil) for physically more correct Single Sheet Testers. The reason was the starting insight that the calculation of the magnetic field strength H(t) from the magnetization current i(t) by a nominal path length LM involves a systematic source of error that impedes correct loss determination, a priori. The main aim of the current paper is to analyze and compare in the literature existing H-coil types. For most accurate measurement, the H-coil should be arranged in zero-distance from the sample surface. The newly developed PCB-H-coils prevail the widespread wire-wound coils in indisputable ways, mainly due to their incompressibility. We present here a coil design that fulfils the corresponding demands in acceptable ways. This is attained by an incompressible H-coil of minimum thickness, extreme coil area and elastic on-press to the sample surface.
This work will place emphasis on the total spaces that were provided by Simmons in [9], and answers an open question of Simmons related to these spaces. The total spaces were suggest by Simmons, but these spaces also arise by using ideas of Gavrilovich in [2], whose characterizes T1 spaces with a categorical lifting property using finite spaces. This point of view of Gavrilovich presents certain advantages in order to see separation axioms using finite frames and generalize or extend the topological concepts to other categories. Moreover, from the categorical definition of total spaces, we show that TTotal frames are an epireflective subcategory of Loc and we give applications of this fact (e.g. there are TTotal frames that are not spatial). Finally, together with total spaces and with a new separation axiom for spaces TS, we answer an open question of H. Simmons about T2 spaces.
We present a first-principles study of Cr-capped Co5/Pd(111) ultrathin films in the near-compensated regime where Co stacking, structural relaxation, and Cr–Co exchange coupling compete on comparable energy scales and jointly determine the magnetic anisotropy. Three representative Co growth stackings are considered: pure fcc, hcp-rich, and mixed fcc+hcp. The hcp-rich stacking is found to be the lowest-energy structure and the most favorable configuration for approaching perpendicular magnetic anisotropy (PMA). We find that the magnetocrystalline anisotropy (MCA) of the non-relaxed films remains in-plane, whereas structural relaxation strongly suppresses the in-plane anisotropy and brings the system close to the spin-reorientation transition (SRT). Within PBE and the magnetic-force-theorem approach, antiferromagnetic Cr–Co coupling shifts the anisotropy toward the perpendicular side and yields the largest positive MCA for the relaxed hcp-rich film. The inclusion of moderate on-site Coulomb corrections through the Ueff parameter further shows that the hcp-rich AF configuration remains the structural ground state, but reveals that the Cr–Co exchange-energy scale and the precise balance between magnetocrystalline and shape anisotropy are Ueff-dependent. Within PBE, inclusion of the dipolar shape-anisotropy term keeps all configurations effectively in-plane. More generally, the results identify Cr/Co5/Pd(111) as a correlation-sensitive system close to a spin-reorientation boundary, rather than as either a universally in-plane film or a robust PMA state. Layer- and k-resolved analyses reveal that this near compensation originates from a competition between buried and middle Co layers, which favor in-plane magnetization, and the upper Pd region, the top Co layer beneath Cr, and the Cr cap, which favor the out-of-plane direction. In reciprocal space, the MCA is governed by the cancellation of positive and negative finite-k hot spots rather than by states near the Γ-point. Fully self-consistent spin–orbit calculations show that the relaxed AF configurations are especially fragile: the frozen-potential approximation overestimates the tendency toward perpendicularity and can even reverse the direction of the easy-axis. Our results identify the relaxed hcp-rich AF Cr/Co5/Pd(111) film as the closest precursor to robust PMA and establish stacking, relaxation, and interfacial exchange as key control parameters for tuning Cr/Co/Pd-based films across the SRT.
Magnetic levitation provides a contactless suspension mechanism for precision measurement and laboratory testing systems where mechanical friction and support interference must be minimised. However, the disturbance response of compact multi-coil maglev platforms remains insufficiently understood. This study experimentally investigates a four-coil electromagnetic levitation platform, focusing on multi-axis suspension behaviour and magnetic force redistribution under external perturbations. Controlled pitch/ roll and yaw disturbances were applied while coil current responses, platform displacement and steady vibration amplitude were measured. The disturbance moment was increased to 0.0172 N·m. Under pitch/roll disturbance, the measured air gap on the disturbed side increased from 24.8 to 26.9 mm, whereas the yaw disturbance produced a smaller air gap change from 24.8 to 25.6 mm. Pitch/ roll disturbances generated greater coil current redistribution and vibration response because they directly modified the vertical suspension force balance, while yaw disturbances were affected mainly by weaker lateral magnetic coupling. The influence of platform mass and nominal air gap on suspension sensitivity is further investigated, demonstrating that reduced air gaps and increased the total weight enhance disturbance sensitivity. These results provide quantitative guidance for the design and performance assessment of magnetic levitation platforms.
The kagome lattice, with its Dirac cones and perfectly flat band arising from destructive interference, represents a promising quantum materials platform for exploring correlated topological phenomena and engineering next-generation quantum devices. Here we investigate the combined effects of Holstein electron–phonon coupling and a perpendicular Zeeman magnetic field on the doped kagome lattice using a full three-band tight-binding model and the one-loop Migdal approximation within the Green’s function formalism. We find that increasing the electron–phonon coupling strongly suppresses van Hove singularities, induces a moderate redistribution of spectral weight near the Fermi level, and shifts the Schottky anomaly in the specific heat to higher temperatures. The Zeeman field splits the spin-dependent bands, including the flat band, leading to enhanced low-temperature susceptibility and non-monotonic field dependence of thermodynamic quantities. Next-nearest-neighbor hopping and staggered potential further tune particle-hole asymmetry without destroying metallicity. These results demonstrate that the flat band dramatically amplifies both electron–phonon and magnetic-field effects. The microscopic insight provides a foundation for understanding the thermodynamic behavior of real kagome materials such as the AV3Sb5 family and offers concrete guidelines for the design of novel quantum devices based on engineered flat-band systems.
Magneto-responsive soft robots urgently demand high-performance magnetic fillers with high saturation magnetization, low coercivity, uniform particle size and dispersibility. In this work, CoTi co-doped M-type barium ferrite BaCoxTixFe12-2xO19 (BCTF) powders were successfully synthesized via a chemical co-precipitation combined with molten salt-assisted calcination. The influences of molten salt proportion and salt-to-precursor ratio on phase composition, microstructure, particle dimension and magnetic performances were systematically explored. The molten salt medium likely shifts the reaction away from sluggish solid-solid diffusion and implies a plausible dissolution-precipitation reaction pathway, effectively suppressing particle agglomeration and improving crystallization quality. Well-crystallized BCTF with regular hexagonal platelet morphology and narrow particle size distribution is obtained after process optimization. The optimized sample delivers a high saturation magnetization of 53.88 emu/g, much higher than 50.85 emu/g of the sample without molten salt, and possesses favorable low coercivity for magnetic actuation. This work provides a facile molten-salt route to fabricate high-performance ferrite powders with optimized magnetic parameters, which exhibit great potential as candidate fillers for magneto-responsive soft actuators in future composite investigations.
In this paper, we answer several open problems in star selection principles posed by Chandra and Alam in (2024, Topology Appl.) and (2024, Rocky Mountain J. Math.). We also present a few related observations.
Amorphous FeSn alloy nanowires with a near-stoichiometric Fe₃Sn₂ composition, serving as a precursor to one-dimensional (1D) kagome magnets, were synthesized via DC electrodeposition into anodic aluminum oxide (AAO) templates with low-temperature annealing (200 °C). For as-deposited nanowires and 200 °C-annealed sample, the magnetic behaviors were similar as the same amorphous characteristics. Room-temperature magnetic measurements reveal a weak uniaxial anisotropy along the wire axis, resulting from the competition between shape anisotropy and stress-induced magnetoelastic anisotropy. Analysis of the angular dependence of coercivity indicates that the magnetization reversal governed by a localized coherent rotation mechanism driven by structural inhomogeneities. Temperature-dependent studies show that saturation magnetization follows Bloch's T3/(Abada et al., 20242) law, while the temperature dependence of coercivity is determined by the competition between thermal activation at low temperatures and spin-wave excitations at higher temperatures. Annealing increases squareness and coercivity due to stress relief and structural homogenization. Although annealing releases stress which reduces the magnetoelastic opposition to anisotropy, the reduction in saturation magnetization—caused by structural relaxation or slight oxidation—leads to a greater decrease in shape anisotropy, ultimately resulting in weaker overall anisotropy. Additionally, the spin-wave stiffness derived from Bloch's constant indicates stronger exchange interactions after annealing.These findings provide fundamental insights into the magnetism of 1D amorphous systems and establish a baseline for the future realization of crystalline kagome Fe₃Sn₂ nanowires.
Solution-phase synthesis has advanced to the point where monodisperse magnetic nanoparticles can now be produced with near-atomic control over size, composition, crystallinity, and interfacial structure. Such precision enables tuning of magnetic ground states, relaxation dynamics, and interparticle interactions, establishing a chemically programmable platform for nanoscale magnetism. This review integrates synthetic design principles with the underlying nanoscale magnetism, including surface anisotropy, spin disorder, finite-size effects, and thermal activation. It illustrates how rational chemical control over metals, alloys, ferrites, and rare-earth nanomagnets enables the control of magnetic properties for potential applications ranging from high-density data storage and exchange-coupled permanent magnets to spintronics, spin-regulated catalysis, magnetic hyperthermia, magnetogenetic neuromodulation, and magnetic resonance imaging. Current progress leads to future direction of magnetic nanopraticle research, including scalable synthesis, robust surface stabilization, controlled assembly, and in-situ observation of magnetic dynamics. The research continues to call for materials chemistry, condensed-matter physics, and device-level engineering to converge to realize the full technological potential of magnetic nanoparticles.
The design of magnetic damping in magnetic thin films is in high demand for the energy-efficient operation of spintronic memory and spin-wave-based devices. Magnetic damping consists of both intrinsic and extrinsic contributions. One of the predominant mechanisms of the extrinsic contribution is two-magnon scattering (TMS), which arises from the inhomogeneity of the internal magnetic field. Recently, it was reported that quasi-periodic spatial magnetic fluctuations (i.e., magnetization ripples) in a ferromagnetic material peak the ferromagnetic resonance linewidth (ΔH) due to TMS at a specific resonance frequency; however, the underlying mechanism is not fully understood. In this study, we examine the dependence of ΔH on grain size and magnetic field orientation in Fe thin films grown on MgO(111) substrates. We observe a clear correlation between the peak feature of ΔH and orientationally dependent grain size, i.e., magnetization ripples. This provides definitive evidence for the mechanism of peak formation triggered by magnon excitations via TMS and magnetization ripples, offering a promising basis for designing magnetic thin films with the necessary magnetization dynamics for use in energy-efficient spintronic devices.
High‑silicon steel is regarded as a promising core material for high-speed motors because of its low high-frequency iron loss. However, its magnetic response to temperature and compressive stress under wide-frequency magnetic-field excitation still requires further clarification. In this study, Fe–6.5 wt% Si high‑silicon steel 10JNEX900 was investigated and compared with Fe–3 wt% Si non-oriented silicon steel ST100 using laminated square specimens. The magnetic flux density and iron loss were measured at 50 Hz, 1500 Hz, and 3000 Hz under separate temperature loading from −50 °C to 150 °C and compressive stress from 0 MPa to 70 MPa. The results show that increasing temperature reduces the magnetic flux density of both materials, with a more pronounced decrease in 10JNEX900. Meanwhile, the iron loss of 10JNEX900 increases with temperature, whereas that of ST100 decreases. In contrast, 10JNEX900 exhibits much lower sensitivity to external compressive stress than ST100. The related mechanisms are discussed in terms of hysteresis-loop variation, classical eddy-current loss, residual loss, and magnetoelastic coupling.
We continue the study of selection principles and open covers using ideals on the set of natural numbers with a focus on the standard ideal orders such as 1-1, Katětov (K) and Katětov-Blass (KB) orders following the works of (Šupina et al., 2016 [34], Šottová et al., 2019 [33] and Šupina et al., 2023 [35]). In addition to the above mentioned ideal orderings we also consider the Rudin-Keisler (RK) and Rudin-Blass (RB) orders and establish the connections among various selection principles related to I-γ-covers, I-large covers and I-groupable covers of X when different ideals on ω are equipped with those orders. We present certain results on selection principles related to I-γ-covers when the ideal I has a pseudounion. Furthermore, we investigate γk and I-γk-covers of X within the framework of ideal order relations and examine connections between the cardinality of the set of all compact subsets of X with certain selection principles using the cardinal invariants such as the slaloms numbers. Finally, it is shown that the I-Hurewicz property of X is equivalent to the Hurewicz property of X when the ideal I has a pseudounion.
A detailed study of depth-resolved magnetization and microstructure of Fe16N2 thin films on MgO (001) and MgAl2O4 (001) substrates and Fe and Cr seed layers is presented. Two aspects of the magnetic properties of Fe16N2 thin films are discussed. First, magnetization enhancement at the interface is observed. Strain and nitrogen deficiency are discussed as possible interfacial mechanisms contributing to this enhancement. Second, the perpendicularly magnetized component (PMC) is identified in Fe16N2 thin films. Correlation with microstructural observations suggests that the PMC is associated with V-shaped grains that are not fully confined within the continuous Fe16N2 layer.
In this work, we examine the combined influence of externally applied electric and magnetic fields on a hydrogenic donor complex confined in a 3D Gaussian GaAs quantum dot. The field dependence of the binding energy is analyzed in detail, and the results show a clear reduction of the binding energy with increasing electric field strength. On the other hand, when the electric field is kept fixed, the magnetic field strengthens the donor binding, indicating a competing interplay between the two external perturbations. The effect of Rashba and Dresselhaus spin-orbit interactions in the presence of both electric and magnetic field is also studied in detail. The magnetic response of the system is also investigated by studying the magnetization and magnetic susceptibility under simultaneous electric and magnetic fields. Both quantities exhibit noticeable field-driven variation, reflecting the strong sensitivity of the donor complex to external control parameters. The present results highlight the tunability of the magnetic and electronic properties of quantum-confined donor systems and may be useful for understanding field-modulated behavior in low dimensional semiconductor structures.
Magnetization rotation in a surface domain wall of a bulk Fe(001) single crystal was studied experimentally using spin-polarized scanning electron microscopy (spin SEM). Owing to the strong magnetostatic energy near the surface, the domain wall exhibits a Néel-type in-plane rotation, although Bloch-type walls are expected in the bulk. Despite this surface modification, the measured domain-wall width agrees well with values calculated from bulk exchange stiffness and magneto crystalline anisotropy constants, indicating that intrinsic bulk parameters govern the wall width even at the surface. Furthermore, a localized reversal in the sense of magnetization rotation was observed within the wall, resembling a Bloch line and suggesting an internal magnetic singularity extending from the bulk to the surface. These results demonstrate that surface-sensitive measurements can provide direct insight into bulk magnetic structures.
