Journal of Superconductivity and Novel Magnetism最新文献

We study the Fermi surface topology of a two-dimensional electron gas (2DEG) proximitized by d-wave superconductors in a linear superconductor–normal–superconductor (SNS) Josephson junction with a (pi) phase difference. Owing to nodal quasiparticles and the anisotropic gap, the d-wave case differs qualitatively from the isotropic s-wave case: the nonlocal conductance is no longer directly tied to the number of critical points on the Fermi surface. Instead, we show that the rectified conductance remains quantized at low bias and faithfully encodes the Fermi surface topology via the Euler number (chi _F). This quantized response persists even for complex or multi-pocket Fermi surfaces, establishing rectified conductance as a robust and experimentally accessible probe of Fermi surface topology in gapless superconductors.

This work addresses the two major bottlenecks hindering the application of Bi2212 high-temperature superconducting round wires: the high technical barrier of the required heat treatment and its prohibitive cost. Our team has broken the heat-treatment bottleneck by independently developing a series of high-pressure heat treatment (HPHT) systems, which are capable of processing coils with bore sizes up to 20 cm and have provided sintering services to multiple research institutions. Concurrently, we have established a full-chain batch fabrication process from precursor powder to coil sintering. We have achieved batch production of Bi2212 wires with single lengths exceeding 1000 m and an annual capacity of 200 km. These wires exhibit a critical current (I_c) ≥ 496 A at 4.2 K and 12 T, and a hysteresis loss as low as 589 mJ/cm³, approaching the ITER standard. For cabling compatibility, strands extracted from cables retained 87.9% to 95.7% of their critical current after bending and straightening. The production scale-up has drastically reduced costs, and these wires have been successfully validated in small coils, Bi2212 CICC conductors, and D-shaped coils, thereby effectively mitigating the two initial challenges and laying a solid foundation for the large-scale application of Bi2212. ✉ Qingbin Hao. HaoQB@c-nin.com. Shengnan Zhang. snzhang@c-nin.com. 1. Superconducting Materials Research Center, Northwest Institute for Non-ferrous Metal Research, Xi’an 710,016, People’s Republic of China. 2. Western Superconducting Technologies Co., Ltd, Xi’an 710,018, People’s Republic of China.

This paper reports a first-principles study on structural, electronic, and magnetic properties of the ZnI₂ monolayers doped with 3d transition-metal (TM) atoms (from Sc to Cu). We investigate the effect of TM substitution on the electronic band structure, density of state, spin polarization, magnetic moment, and charge distribution using spin-polarized density functional theory within the generalized gradient approximation (GGA). The pristine ZnI₂ monolayer is confirmed to be a non-magnetic indirect semiconductor with a band gap of 2.002 eV. We find that the TM doping of ZnI2 can result in various electronic properties: Sc-doping yields a nearly semimetallic gap (0.006 eV), Ti- and Co-doping produce spin-polarized semiconductors with gaps of 0.210 eV and 0.296 eV, respectively; Cr-, Fe-, and Cu-doped systems exhibit half-metallic behavior with band gaps of 0.0006 eV, 0.0014 eV, and 0.0022 eV, respectively. V-, Mn-, and Ni-doped systems lead to bipolar magnetic semiconductors with total gaps of 0.8584 eV, 1.4865 eV, and 0.8407 eV, respectively. The computed magnetic moments increase from 0.89(::{mu:}_{B}) (Sc) to 5.00 (:{mu:}_{B}) (Mn) and then decrease towards 1.00 (:{mu:}_{B}) (Cu) as the 3d orbitals are filled. Overall, these results show a clear and progressive evolution in the system’s behavior from semimetallic to spin-polarized semiconducting, bipolar magnetic semiconducting, and finally half-metallic states, reflecting how the 3d orbital filling systematically modifies the electronic and magnetic characteristics of the ZnI₂ lattice. The spin density indicates the localized or delocalized magnetic behavior of the dopant, and the charge analysis confirms the partial electron transfer, which is related to the occupation of the d-orbital. Such tunable changes in the magnetic and electronic states suggest that 3d transition-metal doping offers a practical pathway to engineer ZnI₂ monolayers for spintronic and magneto-electronic applications.

The ferromagnetic resonance (FMR) behavior of patterned nickel magnonic crystals is shown to be strongly governed by the geometry and thickness of the individual nanostructures. Arrays of square, triangular, and circular nanopillars fabricated by electron beam lithography exhibit a clear inversion in the resonance field order between in-plane (S2 > S1 > S3) and out-of-plane (S2 < S3 < S1) configurations. This inversion arises from the interplay between shape-induced anisotropy and thickness-related dimensional effects. Micromagnetic simulations corroborate the experimental findings, revealing how the dipolar field distribution and edge curvature modulate local magnetization dynamics. The results establish geometry as an efficient tuning parameter for FMR responses in magnonic systems, opening new pathways for the design of spintronic components and high-frequency magnetic devices based on controlled anisotropy engineering.

The structural, magnetic, and dielectric properties of Cr-substituted samarium iron garnet ((S{m}_{3}:F{e}_{5-x}:C{r}_{x}:{O}_{12},:x:=:0.0-0.5)) were systematically investigated to understand the impact of Cr incorporation on the garnet framework. X-ray diffraction analysis confirmed single-phase cubic garnet formation, accompanied by a gradual reduction in lattice parameter and grain size with increasing Cr content. Magnetic measurements revealed two characteristic spin-reorientation transitions in the parent compound, both of which became progressively suppressed upon Cr substitution due to the weakening of (Feleft(aright)-O-Feleft(dright)) superexchange interactions. A consistent decrease in magnetization was observed as magnetic (Fe^{3+}) ions were replaced by lower-moment (Cr^{3+}) ions. Impedance spectroscopy demonstrated clear dielectric relaxation behavior, with relaxation peaks shifting toward higher frequencies for Cr-doped samples that indicates reduced relaxation time and enhanced charge transport. Overall, Cr substitution effectively tunes the magnetic ordering, microstructure, and dielectric response of SmIG, highlighting its potential for multifunctional magneto-dielectric and high-frequency device applications.

This study investigates the role of Fe dopant induced defects in tailoring the physicochemical and functional properties of hydrothermally synthesized BaSnO₃ (BSO) nanostructures. XRD and Raman analyses confirmed the successful incorporation of Fe into the cubic perovskite lattice without the formation of secondary phases. The FTIR spectra further revealed distinct vibrational bands corresponding to Ba–O and Sn–O stretching modes, substantiating the chemical bonding and integrity of the perovskite framework. Morphological analysis showed irregular rod-like nanostructures, indicative of dopant-driven growth modifications. Optical studies revealed Fe-induced modulation of the electronic band structure, resulting in measurable band gap reduction and enhanced defect-related visible emissions in the photoluminescence spectra. Magnetic characterization demonstrated robust room-temperature ferromagnetism in all Fe-doped samples, with M–H loop analysis and ESR measurements confirming oxygen-vacancy–mediated exchange interactions as the origin of magnetization. These findings establish Fe-doped BSO as a multifunctional material that simultaneously exhibits tunable optical band gaps, defect-driven luminescence, and stable ferromagnetism, underscoring its potential for application in dilute magnetic semiconductor–based spintronic and optoelectronic devices.

Two-dimensional heterostructures have become a research focus in materials science, driven by their flexible and adjustable electronic, magnetic, and optical characteristics. As materials with significant potential for optoelectronic and spintronic devices, they exhibit a wide range of application prospects. However, the inherent non-magnetic properties of the SnS₂/MoS₂ heterostructure pose a significant constraint on its potential applications within the realm of spintronics. Therefore, the incorporation of transition metals to impart magnetism is crucial for further expanding the boundaries of spintronic applications. In the present study, we employed first-principles calculations to conduct an in-depth analysis of the photoelectric and magnetic properties of TM/SnS₂/MoS₂ heterostructures, where transition metal (TM = Mn, Fe, Co, Ni, Cu) atoms replace Sn atoms in the heterostructure. The results of the study are as follows: when doped with Mn and Co, the SnS₂/MoS₂ heterostructure exhibits half-metallic properties; when doped with Fe and Cu, it shows characteristics of a magnetic semiconductor; and when doped with Ni, it behaves as a non-magnetic semiconductor. Additionally, the doping of transition metals increases the static dielectric constant and results in the light absorption edge shifting toward longer wavelengths, a phenomenon known as redshift. Therefore, transition metal doping is shown to effectively regulate both the optoelectronic and spintronic characteristics of the SnS₂/MoS₂ heterostructure. The theoretical insights derived from this study lay a foundational framework for the practical deployment of TM/SnS₂/MoS₂ heterostructures in optoelectronic and spintronic technologies, indicating that such heterostructures are promising candidates for high-quality spintronic and optoelectronic devices.

Mono-filamentary and 37-filamentary Bi₂Sr₂Ca₂Cu₃O_10+δ (Bi-2223) superconducting tapes were prepared by the powder-in-tube (PIT) technique. In order to improve the engineering current density (J_e) of the Bi-2223 tape, we tailored the silver/superconductor ratio (Ag/S_c ratio), filaments adhesion and Ag/superconducting interface of the Bi-2223 tapes. The influence of drawing angles (6° & 14°) during the Bi-2223 wire drawing was systematically studied to optimize wire uniformity. It was found that 37-filamentary Bi-2223/Ag wires with a 6° drawing angle didn't merged when the wire diameter reached 1.51 mm. Additionally, the filament area uniformity of wires prepared with a 6° drawing angle was superior to that of wires with a 14° drawing angle. Furthermore, the smaller 6° drawing angle significantly enhanced the filament density of Bi-2223 green wires, thereby affecting the Bi-2223 phase formation rate. Owning to increase of filament density and improvement Ag/superconducting core interface, the critical current density (J_c) value increase from 23.6 kA/cm² to 27.1 kA/cm².

This study investigates the superconducting properties of MoRe films deposited by DC magnetron sputtering with a composite target consisting of 56 at.% Mo and 44 at.% Re on sapphire substrates at room temperature. All films are passivated with a silicon capping layer. The focus of this study is on the thickness dependence of the critical temperature (T_textrm{c}(d)). The electrical transport measurements show a direct correlation between (T_textrm{c}) and disorder, quantified by the Ioffe-Regel parameter, (k_Fl). The parameter ranges from 6 for 3 nm films to 20 for 100 nm, while (T_textrm{c}) varies from 6 K to 8.4 K, respectively. The analysis suggests that the films exhibit a moderate level of disorder, and the (T_textrm{c}(d)) dependence can be explained by a fermionic mechanism related to (k_Fl) rather than the sheet resistance of the film, (R_s).

The precise and local manipulation of perpendicular magnetic anisotropy (PMA) and the interfacial Dzyaloshinskii-Moriya interaction (iDMI) is paramount for the development of skyrmion-based spintronic devices. While light-ion irradiation has been explored for magnetic property modification, the use of heavy ions offers a pathway for enhanced interfacial intermixing and potentially decoupled control of these key parameters. Here, we demonstrate that defocused Ga⁺ ion beam irradiation acts as a powerful tool for the graded, local tuning of magnetic properties in Ru/Co/W/Ru multilayers. We achieve a continuous transformation of the magnetic domain structure, from labyrinthine stripes to isolated sub-micrometer skyrmion bubbles, by selectively varying the irradiation fluence. Crucially, we find that PMA and iDMI exhibit distinct degradation rates upon irradiation, with the anisotropy energy decreasing fourfold while the iDMI strength is halved, enabling a widened window for skyrmion stabilization. Micromagnetic simulations, calibrated with experimental parameters, confirm the formation of nanoscale skyrmions (~ 130 nm) at high fluences where direct optical observation is limited. Combined experimental characterization and first-principles calculations reveal that this decoupling stems from Ga⁺-induced interfacial alloying, which disproportionately affects the interface-sensitive origins of PMA and iDMI. This work establishes defocused ion beam irradiation as a versatile nanofabrication technique for designing two-dimensional magnetic metasurfaces and prototype race-track memory devices.