Journal of Superconductivity and Novel Magnetism最新文献

Herein, we report a fundamental study revealing the substantial change in magnetic and electrical properties promoted by manganese (Mn) substitution in the iron (Fe) site of double perovskite LaYFe₂O₆ [LaYFe_2-xMn_xO₆; x = 0, 0.05, 0.10, and 0.15], which is prepared by the sol–gel auto-combustion method. The structural, morphological, magnetic, and electrical properties of all the samples are investigated to explore the influence of Mn in the compound. X-ray diffraction (XRD) study reveals the confirmation of phase formation with orthorhombic crystal structure having symmetries P2₁nm and Pbnm (small contribution). X-ray photoelectron spectroscopy (XPS) analysis corroborates the mixed valence state of Fe and Mn, while the dominancy of + 3 oxidation state can be confirmed for them. Magnetization study reveals that the transition temperature reduces drastically (~ 100 K) by the Mn substitution and approaches toward room temperature (RT). At 573 K, the maximum magnetization value enhanced up to ~ 30% by the Mn substitution. Grain boundary contribution in the electrical response is more prominent in the higher Mn content samples. The application of DC magnetic field exhibits a significant influence on the impedance spectra due to the substitution of Mn in the lattice, which corroborates the signature of magnetoelectric (ME) coupling. The presence of ME coupling is further confirmed by the direct magnetoelectric measurement. This finding along with the above RT magnetic transition could make it a feasible candidate for ME-based applications.

In this research, a novel method to improve the particle size and content of Y₂BaCuO₅ (Y-211) in YBa₂Cu₃O_7 − x (YBCO) bulks was demonstrated. The single-domain YBCO bulks (20 mm in diameter) have been fabricated employing the RE+011 TSIG technique with different heating rates during the liquid phase infiltration (LPI) stage. The various heating rates on Y-211 size and its content in the final YBCO samples has been investigated in detail. The findings suggest that the average size of the Y-211 particles in the Y-123 matrix initially decreases followed by an increase, while its volume fraction gradually decreases with increasing heating rate. Furthermore, it is observed that the levitation force and the trapped fields exhibit an initial increase followed by a subsequent decrease as the heating rate increases. Among all the samples, sample S3 (heating rate of 30 °C/h) has the best magnetic levitation force and trapped field performances at 77 K, i.e., the largest values are of 45.3 N and 0.41 T, respectively. The results suggest that, while employing the RE+011 TSIG technique for YBCO bulk fabrication, the average size and volume fraction of Y-211 particles in the final sample can be further enhanced by controlling the heating rates during the LPI stage, obviating any need for chemical refining agents.

When a non-equilibrium excitation (a non-paired electron) is injected into a superconductor, it can travel fairly large distance before forming an equilibrium Copper pair. Here, we fabricated and experimentally studied electron transport in a solid-state analogue of a two-slit optical interferometer: T-shaped normal metal electrode (copper) — dielectric tunnel layer (aluminum oxide) — superconducting fork (aluminum). If the perimeter of the interferometer loop is sufficiently small, the phase of the non-equilibrium quasiparticle wave function is preserved and can be adjusted utilizing the Aharonov-Bohm effect. The coherent contribution manifests itself as non-monotonic dependence of the tunnel current on perpendicular magnetic field.

Magnetic thin films with fast magnetization switching and low Gilbert damping are crucial for devices working at high frequency with low power consumption. In this work, composition-controlled high-quality Fe–Ni alloy thin films were electrodeposited on ITO/glass substrates and their magnetization switching behavior was investigated using MOKE and FMR. The phase of deposited alloy transformed from FCC to mixed BCC and FCC for high Fe content films. All the deposited alloy films display granular morphology and possess soft magnetic characteristics with low coercivity (H_c < 50 Oe). Magneto-optic Kerr effect hysteresis along with simultaneous domain imaging reveals that the alloy composition influences anisotropy, domain structure, and magnetization switching process. The alloyed films exhibited fourfold surface anisotropy. The magnetization reversal in pure Fe and Ni samples occurs through stripe-like domains, whereas band and ripple-like domains were evident for the alloyed films. Fast magnetization switching within a minimum field range of ~ 3 Oe was observed for Fe₂₅Ni₇₅ sample. The ferromagnetic resonance measurements revealed that the Fe₂₅Ni₇₅ alloy films exhibit lowest Gilbert damping (α = 0.024) compared to pure Fe and Ni films. In summary, these findings offer valuable insight for tailoring the magnetic properties of Fe–Ni alloy thin films with appropriate alloy composition.

In this contribution, we studied the magnetization, magnetic susceptibility, and electronic superconducting density of a superconducting irregular octagon in the presence of an external magnetic field H. We solved the time-dependent Ginzburg-Landau equations (TDGL) for a one-band condensate for a mesoscopic type-I sample ((kappa <1/sqrt{2})). Our results show the existence of Shubnikov-vortices in the up-branch of the magnetic field (H). Also, we found a paramagnetic response in descending field. We think that the vortex state proposed here reflect intrinsic features of the superconducting sample.