Journal of Superconductivity and Novel Magnetism最新文献

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.

The in-situ Cu-7.7Nb microcomposite (MC) wires have been studied at different drawing stages before and after intermediate annealing. It is demonstrated that both deformation and intermediate annealing of the MCs are accompanied by a noticeable change in the Nb/Cu interface density, which affects not only the strength, but also the electrical conductivity of the composite wire. The intermediate annealing temperature affects the conductivity of the wire at all stages of deformation that follow the annealing. The wire has the maximum conductivity after annealing at 800 °C. Based on scanning and transmission electron microscopy data, dependences of the Nb filament thicknesses, their aspect ratios, and interface densities on the composite strain have been constructed. The change of the Nb filaments morphology under intermediate annealing is accompanied with a decrease in the Cu/Nb interface density, the latter being a factor responsible for the increase in composite conductivity under annealing. Conductivity increases with increasing annealing temperature. These differences are preserved throughout the entire deformation process up to the final wire diameter of 0.05 mm.

This study presents a comprehensive first-principles investigation of the structural, elastic, electronic, magnetic, optical, and thermoelectric properties of hexagonal ThX₅ compounds (X = Fe, Ni) using Density Functional Theory (DFT) within the GGA + U framework. The elastic constants and 3D mechanical property visualizations demonstrate strong anisotropy in ThFe₅, making it suitable for directional mechanical applications, while ThNi₅ displays more isotropic behavior, favoring uniform load-bearing roles. In addition, electronic structure analysis, including TDOS, PDOS, and band structures, confirms the metallic and magnetic nature of both materials, with ThFe₅ exhibiting stronger ferromagnetism due to higher magnetic moments and larger spin splitting. These magnetic features significantly influence transport and optical properties. The optical analysis, based on complex dielectric functions, reveals strong direction-dependent optical responses, with plasma frequencies and reflectivity spectra confirming metallic behavior in both compounds. Notably, ThFe₅ shows higher anisotropies in optical conductivity and extinction coefficients than ThNi₅. Furthermore, thermoelectric performance, evaluated using Boltzmann transport theory, exhibits distinct temperature-dependent behavior in the Seebeck coefficient, electrical conductivity, and power factor. ThFe₅ displays a complex spin-dependent thermoelectric response with a temperature-induced carrier-type crossover, while ThNi₅ shows a stable p-type dominance at higher temperatures.

A series of Mn-doped CaKFe₄As₄ samples, CaK(Fe_1 − xMn_x)₄As₄ with x values of 0, 0.005, 0.01, 0.02, 0.03, 0.04, and 0.05, are synthesized using two distinct routes: conventional synthesis process at ambient pressure (CSP), and high gas-pressure and high-temperature synthesis (HP-HTS) method. Comprehensive characterizations are performed on these samples to investigate their superconducting properties. This study examines the effects of Mn substitution at Fe sites in the FeAs layer on the superconducting properties of the CaKFe₄As₄ (1144) material. The HP-HTS process improves the microstructure and phase purity of the parent sample (x = 0), resulting in an enhanced superconducting transition temperature (T_c). In contrast, Mn doping via the CSP method in CaKFe₄As₄ reduces the sample quality and superconducting performance. Notably, the high-pressure synthesis method leads to an increase in the T_c by 3 to 7 K, particularly at low Mn concentrations. While the critical current density (J_c) of the parent sample (x = 0) shows a significant enhancement under the applied magnetic fields, J_c decreases for Mn-doped CaKFe₄As₄ bulks. These results demonstrate that high-pressure synthesis is an effective approach to improve the superconducting properties of Mn-doped 1144 compounds.

The SrFe_{12 − 2x}(CoSn)_xO₁₉ (x = 0.1 and 0.3) hexaferrites and their [y(SrFe_{12 − 2x}Co_xSn_xO₁₉)+(1 − y)PLA] (y = 0.0–1.0) composites were synthesized via solid-state reaction assisted by high-energy milling and melt-compression. X-ray diffraction (XRD) and Rietveld refinement confirmed the magnetoplumbite structure with minor α-Fe₂O₃ and CoFe₂O₄ phases (≤ 14 wt%) at x = 0.3. Lattice parameters expanded slightly (a = 5.884 to 5.892 Å; c = 23.06 to 23.09 Å), accompanied by crystallite growth (τ ≈ 57.5→61.3 nm) and microstrain increase (ε = 0.09→0.12%). Saturation magnetization (Ms) varied nonlinearly with doping, decreasing to 216 × 10³ A·m⁻¹ at x = 0.1, then rising to 259 × 10³ A·m⁻¹ for x = 0.3, while coercivity (Hc) dropped from 204 × 10³ to 65 × 10³ A·m⁻¹. The effective anisotropy constant (K_eff) ranged 2.3–3.2 × 10⁵ J·m⁻³ and the anisotropy field (Ha) 1.46–1.67 × 10⁶ A·m⁻¹. For SrMCoSn/PLA composites, XRD revealed coexistence of amorphous PLA and hexaferrite phases, with ferrimagnetic response emerging from y ≥ 0.1. Mₛ increased from 3.4 × 10³ to 59.7 × 10³ A·m⁻¹ as y rose to 0.6, whereas Hc remained nearly constant (~ 2 × 10⁵ A·m⁻¹) up to y = 0.5, decreasing thereafter. The linear rise of Ha (2.45 to 2.60 × 10⁷ A·m⁻¹) with ferrite fraction highlights the interfacial magnetic coupling within the polymer matrix. These results demonstrate tunable structural and magnetic properties in Co-Sn-doped SrM/PLA composites, enabling their application in magnetically responsive and multifunctional materials.