Journal of Superconductivity and Novel Magnetism最新文献

The global transition to a sustainable energy economy faces fundamental constraints in electrical infrastructure, energy storage, and high-power-density machines. Existing power grids are inadequate for integrating intermittent renewable generation, while the decarbonization of transport and industry necessitates breakthroughs in electric motor and generator technology. Superconductivity, offering lossless power transmission and high-field magnetics, has been a long-held technological goal, but its large-scale implementation has been critically constrained by the supply volatility and prohibitive cost of its primary cryogen, liquid helium. This paper posits that liquid hydrogen (LH₂) is the critical enabler to overcome this barrier. At its boiling point of 20 K, LH₂ serves as an ideal cryogen for modern metallic (e.g., MgB₂) and oxide (e.g., REBCO) superconductors, which exhibit their optimal performance parameters in this temperature regime. This paper details the “Hydrogen Cryomagnetics” platform, a synergistic integration of superconductivity and hydrogen energy vectors. We analyse its transformative applications in grid-scale transmission (hybrid H₂ electric “SuperCables”), rotating machines (the fuel-as-coolant paradigm for electric aviation), grid stabilization (LH₂-cooled SMES), and compact fusion energy. This synergy positions superconductivity as a practical, scalable, and essential pillar of a decarbonized energy infrastructure.

In this paper, the stability characteristics, electronic configuration, magnetic coupling mechanism, and optical properties of ZnS/ZnO heterojunctions doped with Cu²⁺ and containing point defects (V_Zn/V_O/V_S) were systematically investigated using first-principles calculations. Studies have shown that under Zn-rich conditions, the O-Zn interface containing oxygen vacancies (V_O) achieves the highest stability, while under Cu-rich conditions, both O-Zn and S-Zn interfaces are viable. The O-Zn interface outperforms the S-Zn interface in both structural stability and band gap reduction capability. Cu²⁺ doping on the ZnO side induces a more pronounced band gap narrowing effect than that on the ZnS side. The synergistic interaction between vacancy defects (V_Zn/V_O/V_S) and Cu²⁺ doping further narrows the band gap, with the minimum value reaching 1.23 eV. In the Cu²⁺-doped O-Zn interface system containing V_O/V_Zn, the average ratio of the effective mass of holes to electrons ((:stackrel{-}{D})) can be achieved in the range of 1.58–1.83. A balance between light absorption and carrier separation is enabled by its moderate band gap (2.01–2.47 eV), and the carrier separation efficiency is significantly enhanced. Furthermore, the visible light absorption edge of the system is redshifted to 692 nm, with the maximum absorption coefficient reaching 2.45(:times:)10⁵ cm ^− 1. Magnetic analysis reveals that the magnetic core of the system is the unpaired electron of Cu²⁺-3d⁹. During the charge compensation process between V_O/V_S and Cu²⁺, electrons are confined within the Cu-S coordination layer by the strong hybridization of Cu−3d and neighboring S−3p orbitals, as well as Coulombic attractive forces. The spin polarization effect is only manifested in this local structure. The strong electronegativity of the O-Zn interface partially suppresses the spin polarization of S−3p orbital electrons, with the net magnetic moment of the system maintained at 1–2 (:mu:)_B. In contrast, the weaker electronegativity of the S-Zn interface leads to reduced suppression of spin polarization, allowing the net magnetic moment to reach 4 (:mu:)_B.

Study of critical phenomena in materials is both fundamentally important and provides a large scope for various applications. In this work, we have investigated the nature of ferromagnetic-to-paramagnetic phase transition and critical behaviour around the magnetic phase transition temperature of La_0.67Ca_0.33−xBa_xMnO₃ (x = 0, 0.08, 0.13, 0.23 & 0.33) compounds with the help of Modified Arrott Plot method. Further, analysed the results by comparing the choice of critical exponents obtained from modified Arrott plot with those of field dependent change in magnetic entropy (ΔS_M). It is observed that starting with x = 0.08, a second-order ferromagnetic-to-paramagnetic phase transition is exhibited by these compounds. At lower Ba content (x = 0.08) the magnetic interactions present in the materials are well described by Mean field tricritical model whereas with increasing Ba content at Ca site, 3D nearest neighbor Heisenberg model appears to be more appropriate model describing the magnetic interactions present.

The ability to design magnetic anisotropy in one-dimensional nanostructures is a cornerstone of modern spintronics and data storage. Typically, the high aspect ratio of nanowires dictates a dominant shape anisotropy with an easy axis parallel to their length. Here, we demonstrate a dramatic reversal of this paradigm in composition-gradient Co-CoW nanowires. Using a tailored electrodeposition process, we fabricate nanowires with a smooth transition from crystalline hcp-Co at the base to an amorphous CoW alloy. Structural and elemental analysis confirms the controlled longitudinal gradient. Strikingly, magnetic characterization reveals an easy magnetization plane perpendicular to the nanowire long axis, a direct inversion of the conventional easy-axis orientation observed in homogeneous Co or CoW nanowires. This gradient-induced anisotropy is accompanied by a significant enhancement of transverse coercivity up to 250 Oe. The anisotropy field distribution and first-order reversal curve (FORC) analysis reveal a multiphase magnetic system where the magnetization switching is governed by coherent rotation and localized domain wall motion, driven by internal magnetostatic and magnetoelastic effects originating from the composition gradient. Our findings establish compositional grading as a powerful tool for designing unconventional magnetic anisotropies in functional nanomaterials.

In order to study the characteristics of electromagnet, this paper present an electromagnet used in track-change-interlocking mechanism of three-dimensional braiding machine. When the slider proper connection, the electromagnet begins to work, its electromagnet force should bigger than the impact force of slider and carrier base. The force analysis of carrier base is conducted by mathematical method, the electromagnet model is simulated in the COMSOL Multiphysics simulation software, get the surface of electromagnet, magnetic vector potential of electromagnet and electromagnetic force the electromagnet. Then use ADAMS software to simulate the carrier base crash to the chassis, get the max impact force during track change process. The impact force is 3.26% less than electromagnet force, indicate that the electromagnet can used in track-change-interlocking mechanism of three-dimensional braiding machine. Use the experiment to validate these models, the results show that the experiment is basically consistent with the simulation and can prove the accuracy the simulation.

Cesium based double perovskites are important for their tunable optoelectronic attributes, magnetic ability, stability, and lead-free composition, making them promising materials for sustainable photovoltaic and spintronic applications. We have examined in detail the physical characteristics of the cubic Cs₂LiMoBr₆ double perovskite. The structural stable phase is verified through the structural stability parameters. Furthermore, information about the interaction of material with electromagnetic radiation is revealed by the optical properties. The optical characteristics predict their peak response in the UV range. A direct bandgap has been measured with a spin-up of 2.25 eV and a spin-down of 3.56 eV. Based on the magnetic moments of 3.00173 µB, Cs₂LiMoBr₆ is a promising material for use in spintronic devices. The transport traits are also assessed, presenting large ZT values at high temperatures for spin-up and large ZT at low temperatures for spin-dn. Based on the aforementioned characteristics, Cs₂LiMoBr₆ is a reasonable choice for optoelectronic, thermoelectric and spintronic applications.

This study presents a comprehensive first-principles investigation of the electronic, magnetic, and structural properties of manganese-doped zinc oxide (Mn_xZn_1-xO) using Density Functional Theory (DFT) with the Local Spin Density Approximation and Hubbard U correction (LSDA + U). By modeling supercells ranging from 32 to 192 atoms, we systematically analyzed the effects of Mn concentration (from 1.04% to 12.5%). The electronic structure calculations reveal that Mn doping induces significant spin polarization. At low concentrations (≤ 6.25%), the system behaves as a spin-split semiconductor, with the calculated spin-down band gap for ~ 2% Mn doping (3.54 eV) showing excellent agreement with experimental photoluminescence data (3.53 eV). In contrast, at a high concentration of 12.5%, the system transitions to a metallic state. Magnetic property analysis shows that each Mn dopant introduces a localized magnetic moment of approximately 4.8–4.9 µ_B, consistent with a high-spin Mn²⁺ state, and induces minor spin polarization on neighboring oxygen atoms, indicating p-d hybridization. Our calculations reveal a delicate competition between ferromagnetic (FM) and antiferromagnetic (AFM) ordering, with the magnetic ground state alternating as a function of Mn concentration. Stability analysis, based on formation and cohesive energies, confirms that Mn substitution in the ZnO lattice is thermodynamically favorable and structurally stable across all concentrations studied. However, the Curie temperatures estimated for the FM-stable configurations are very low (< 4 K). These findings suggest that while Mn-doped ZnO is structurally stable and possesses tunable spin-polarized electronic properties, it is intrinsically paramagnetic at room temperature in its pristine, defect-free form. Achieving robust ferromagnetism likely requires extrinsic factors such as defect engineering.

Chalcogenide perovskites have recently emerged as a promising family of functional materials owing to their tunable electronic structures, chemical stability, and potential in thermoelectric, optoelectronic, and protective-coating applications. In this work, we present a comprehensive first-principles investigation of the structural, mechanical, thermal, electronic and optical properties of the chalcogenide perovskites BaTaS₃ and BaNbS₃ using density functional theory (DFT). The optimized lattice parameters for BaTaS₃ (a = 6.948 Å, c = 5.709 Å) and BaNbS₃ (a = 6.932 Å, c = 5.749 Å) agree well with available literature. Both compounds crystallize in the orthorhombic phase and exhibit metallic electronic characteristics. The calculated elastic constants satisfy the Born stability criteria, confirming their mechanical stability, while moderate elastic anisotropy is observed from the directional dependence of Young’s modulus. The evaluated bulk, shear, and Young’s moduli reveal that BaNbS₃ is mechanically stiffer than BaTaS₃. The Debye temperatures were estimated to be 309.2 K (BaTaS₃) and 330.8 K (BaNbS₃), while the minimum lattice thermal conductivities were calculated as 2.7 and 2.88 W m⁻¹ K⁻¹, respectively. Optical analysis reveals high reflectivity (> 65%) in the visible–UV region and pronounced plasma resonance peaks at ~ 15 eV. These quantitative results position BaTaS₃ and BaNbS₃ as promising chalcogenide perovskites for thermal-management and reflective-coating applications. Optical properties including the dielectric function, absorption coefficient, reflectivity, and energy-loss spectra were analyzed up to 50 eV, revealing strong metallic reflectivity and a pronounced plasma resonance in the ultraviolet region. These results provide a detailed understanding of the intrinsic physical properties of BaTaS₃ and BaNbS₃ and establish them as representative members of the chalcogenide perovskite class for future theoretical and experimental exploration.

The physical, morphological, optical, and magnetic characteristics of zinc oxide (ZnO) nanoparticles co-doped with yttrium (Y) and neodymium (Nd) are examined in this work. The nanoparticles are synthesized using the co-precipitation technique with and without the addition of ethylenediaminetetraacetic acid (EDTA). For structure identification, X-ray diffraction (XRD) was used. The hexagonal wurtzite structure of ZnO was verified with successful Y and Nd inclusion, as well as a discernible decrease in crystallite size from 25.71 nm (x = 0) to 20.78 nm (x = 0.04) in uncapped samples, and from 32.72 nm (x = 0) to 18.46 nm (x = 0.04) in samples added with EDTA. Because of EDTA’s capping properties, morphological analyses using transmission electron microscope (TEM) showed that the EDTA-ZnO samples contained smaller, more homogeneous particles. Band gap narrowing and an absorption edge redshift were detected by UV-Vis spectroscopy, indicating changed optical behaviour, with extracted band gaps varying between 2.46 and 2.88 eV for uncapped and 2.71–2.89 eV for EDTA-capped systems. An agglomerated non-homogeneous morphology combining spherical and needle-like forms was observed in co-doped samples. Fourier transform infrared spectroscopy (FTIR) was used to confirm the vibrational characteristics. Because of the O-H group present in the EDTA molecules, EDTA-capped ZnO samples also had an extra OH vibration band and an additional ester carbonyl band at 1745 cm^− 1 due to EDTA coordination. Co-doped and EDTA-modified materials showed a reduced band gap and a redshift in absorption, according to UV-Vis spectroscopy. Vibrating sample magnetometer (VSM) magnetic studies revealed weak room-temperature ferromagnetism with saturation magnetization varying from 32.4 × 10^− 3 emu/g (x = 0) to 18.419 × 10^− 3 emu/g for x = 0.04 for uncapped samples, while EDTA-capped samples reached 39.43 × 10^− 3 emu/g at x = 0.04, indicating enhanced magnetic response due to oxygen-vacancy concentration and dopant interaction.