Journal of Superconductivity and Novel Magnetism最新文献

We report a novel chemical methodology for the synthesis of nanocrystalline CoWN₂ which is stabilized by the induction effect. The methodology involves the nitridation of sol-gel-derived CoWO₄ precursor in nanocrystalline form using gaseous NH₃(g). We could obtain CoWN₂ as a nitrided product at both 700 °C and 750 °C with varied crystallinity. The synthesized materials were characterized using XRD, FESEM, EDS, and magnetic measurements. XRD studies confirm hexagonal CoWN₂ phase formation with a minor impurity phase which comprises of metallic Co. We have noted the values of lattice constants of CoWN₂ materials, i.e., a = 2.876(7) Å, b = 2.876(6) Å, c = 15.372(48) Å, and a = 2.872(3) Å, b = 2.872(2) Å, and c = 15.381(21) for the products synthesized at 700 °C and synthesized at 750 °C, respectively. The crystallite sizes are calculated as 11 ± 0.5 nm for CoWN₂ nanomaterials synthesized at 700 °C whereas 16 ± 0.5 nm for CoWN₂ nanomaterials synthesized at 750 °C. FESEM micrograph studies of CoWN₂ nanomaterials show nearly spherical particles. The average particle sizes obtained from FESEM images are 90 ± 5 nm for the nanomaterials obtained at 700 °C and 45 ± 2 nm for those obtained at 750 °C. Room temperature magnetic parameters, i.e., M_s and H_c for CoWN₂ materials synthesized at 700 °C are found to be 1.49 emu/g and 389 Oe, respectively, whereas for CoWN₂ materials (synthesized at 750 °C), the values marginally reduce to 0.06 emu/g and 375 Oe, respectively.

The nanocrystalline composition of Zn_0.95Co_0.02Mo_0.03O revealed advanced and promising multifunctional characteristics for data and energy storage applications as well as environmental pollution treatment. Pure ZnO, Zn_0.97Co_0.02Mo_0.01O, and Zn_0.95Co_0.02Mo_0.03O samples were simply synthesized at 400 °C. For all samples, all X-ray diffraction (XRD) peaks were perfectly assigned to the zinc oxide (ZnO) compound with hexagonal structure. The relation between the ionic size of Zn²⁺, Co²⁺, and Mo⁴⁺ ions, shift of XRD peaks, and variation of unit cell volume evidenced the actual substitution process. The insertion of Co²⁺ and Mo⁴⁺ ions spread the optical response of ZnO to the visible light spectrum by reducing its band gap energy from 3.25 to 2.9 and 2.8 eV. The scanning electron microscopy (SEM) micrographs of both codoped Zn_0.97Co_0.02Mo_0.01O and Zn_0.95Co_0.02Mo_0.03O samples display the formation of particles with sheets shaped like rose leaves and fine spherical particles. Magnetically, the composition of Zn_0.95Co_0.02Mo_0.03O exhibits a strong ferromagnetic order at room temperature with perfect hysteresis loop nature and a high saturation magnetization of 1.11 emu/g. For energy storage uses, Zn_0.97Co_0.02Mo_0.01O and Zn_0.95Co_0.02Mo_0.03O samples exhibit a colossal dielectric constant (relative permittivity) of 11,560 and 21,019 at low frequency, respectively. The incorporation of (Co, Mo) significantly improved the sunlight-photocatalytic performance of the ZnO catalyst for depollution of stable Reactive Blue 19 (RB19) dye, leading to a total photodegradation efficiency of 98% in 75 min. In addition, the Zn_0.95Co_0.02Mo_0.03O photocatalyst has a high stability for recyclability and a high ability to mineralize the RB19 dye to CO₂ and H₂O.

Graphical Abstract

High-temperature superconducting (HTS) cable, with massive current carrying capability and low electric power loss, is always at the cutting edge of the strong electric fields. The concentric three-phase HTS cable usually subjects to the impact of electromagnetic and mechanical forces. The forces will lead to the shape change of the cable, which may damage the cable and cause the degeneration of the critical current (Ic). In this paper, an analysis model of stress-strain and bending properties of the 10 kV/1 KA cable based on laminated theory is built. Laminated beam theory can simplify REBCO superconducting tape and concentric three-phase HTS cable to analyze stress-strain distribution. A finite element method (FEM) simulation model is established to analyze the critical bending radius of the HTS cable. Meanwhile, the normalized of the critical current of the cable is obtained at different bending radii. The analysis results will provide the theoretical basis for cable pipelaying and line relay protection in grid.

This study investigates the influence of sintering temperature on the structural and magnetic properties of Y₃Fe_4,97La_0,03O₁₂, elucidating the nucleation and growth mechanisms related to temperature. Through meticulous X-ray diffraction analysis, we confirmed the formation of a single YIG phase at 900 °C. Conversely, samples sintered at 1000 °C and 1100 °C reveal the presence of a second phase, attributed to YFeO₃, highlighting the complex interaction between sintering temperature and material morphology. Moreover, magnetic characterization details how sintering temperatures directly influence the magnetic moment and saturation magnetization of the nanoparticles, presenting significant fluctuations in magnetic properties due to the presence of the secondary phase. This work not only sheds light on the subtle relationship between lanthanum doping, sintering temperature, and the resulting magnetic properties but also paves the way for fine-tuning these properties in advanced materials for specific technological applications.

Various experimental methods are used to examine the effect of cooling rate on the magnetic properties of magnetic materials, such as melt spinning at different wheel speeds. To shed light on these experimental studies as a theoretical study, we used a mixed spin (1, 3/2) Ising system on a square lattice under an oscillating magnetic field within the path probability method. It is very advantageous to use the path probability method in such studies, because it explains the dynamic magnetic phase behaviors and dynamic hysteresis curves of the system depending on all system parameters, and one of the coupling parameters (({k}_{2})) arising in this method corresponds to the wheel speed (rate constant) in the melt spinning method. In this study, dynamic hysteresis curves of a magnetic material were obtained for different ({k}_{2}) parameters as well as other system parameters, namely reduced temperature, crystal field interaction, and angular frequency. In some magnetic materials, hard and soft magnetic hysteresis loop behaviors and single and multiple hysteresis loop behaviors have been obtained, which have been reported theoretically as well as experimentally. The results shed light on experimental workers who were unable to reach higher wheel speeds using the melt-spinning method.

The structural parameters and harmonic conditions detection of superconducting transformer are studied in this paper. And a two-dimensional axisymmetric model of a single-phase 10 kVA HTS transformer is developed using the finite element H-formulation. The study involves determining the optimum structural parameters of the HTS transformer, calculating the AC losses, and analyzing the corresponding trends. In addition, the effect of different distortion currents on the operating state of the HTS transformer under harmonic conditions is investigated. The results show that the primary-secondary winding spacing is negatively correlated with the AC losses. In addition, the influence of harmonic conditions on AC losses mainly depends on the amplitude of the input current, and the higher the total harmonic distortion, the more serious the current waveform distortion, the more likely to produce a temperature surge, thus affecting the operational stability of superconducting transformers. The research results in this paper can provide a reference for the design and operational stability of HTS transformers.

This research aims to employ a first-principles approach based on density functional theory (DFT) to predict the structural, electronic, and magnetic attributes of (CdMX) compounds, where (M) represents (Ru), (Rh), or (Pd), and (X) represents either (S) or (Se). We utilized the modified Beck-Johnson potential, combined with the generalized gradient approximation ((mBJGGA)), to scrutinize the electronic and magnetic features of these compounds. The results reveal robust magnetic ground states for (M)-doped (CdX). The analysis of spin-polarized band structures and densities of states indicates that (CdRuX) and (CdPdX) compounds exhibit half-metallic ferromagnetism, characterized by complete spin polarization of 100% at the Fermi level. Conversely, (CdRhX) compounds exhibit the properties of ferromagnetic semiconductors. For (Ru), (Rh), and (Pd)-doped (CdX), an integer-integrated total magnetic moment is observed, corresponding to 4, 3, and 2 ({mu }_{B}), respectively, with the primary contribution stemming from the doping atom and its four nearest neighboring (X) atoms. This ferromagnetic behavior is attributed to the strong (p)-(d) hybridization occurring between the states of the host (X) ions and the (M) impurity ion. Consequently, the outcomes of our study render these alloys as suitable materials for possible spintronic devices.

In this work, the effect of intrinsic doping of YGBCO target density on superconducting thin films is systematically discussed. YGBCO superconducting films generated with varying densities of YGBCO targets are all pure C-axis orientated after process optimization, but the crystallinity of the films varies, and the crystalline property of the superconducting films developed from the target with the lowest density is the best. YGBCO films made with the best density objective had in-plane and out-of-plane textures of 3.5° and 1.4°, respectively. Thin film surface morphology is affected by the density of the target material; the minimal surface roughness can be as low as 5.5 nm, The critical current of YGBCO film prepared by target with the minimum density is 135 A, and the greatest current density is 5.4×(10^6) (textrm{A}/textrm{cm}^2). At 4.2 K and 9 T, the critical current of the thin film created with the intrinsically nailed YGBCO target can reach 338 A. This paper prepares a 530-m-long second-generation high-temperature superconducting tape with the optimized parameters. The current of the long tape is 380 A, and the current density is 4.2×(10^6) (textrm{A}/textrm{cm}^2).