Journal of Superconductivity and Novel Magnetism最新文献

The present work reports the magnetic and structural behavior of [Gd/Co]₁₀ multilayers with different Co thickness values, prepared by magnetron sputtering, as a function of thermal annealing. Intermixing is observed with thermal annealing for all the samples; however, complete intermixing is not observed even after annealing at 773 K. Antiparallel alignment of Gd and Co layer magnetization is observed for pristine samples from room temperature X-ray magnetic circular dichroism measurements. Magnetic compensation temperature is found to vary depending on the thickness of Co layers. Temperature-dependent magneto-optical Kerr effect (MOKE) measurements depict the inversion of loops across magnetic compensation temperature for all the pristine samples. However, no signatures of magnetic compensation are observed in the low-temperature MOKE loops for the annealed samples. MOKE loops of the annealed samples exhibit double hysteresis loops. The results are explained in terms of intermixing with annealing.

The present work focusses on the green synthesis of Co₃O₄ nanoparticles (NPs) using Lepidagathis ananthapuramensis leaf extract and to investigate its structural, optical, morphological and magnetic properties. The structural information confirmed the formation of spinel type polycrystalline cubic symmetry with space group Fd-3 m. The Fourier transform infrared spectroscopic studies revealed the sharp doublet peak in the finger print region pertaining to the Co²⁺ and Co³⁺ ions. The X-ray photoelectron spectroscopy further confirmed the presence of Co³⁺ and Co²⁺ ions in which Co³⁺ ions are present more than Co²⁺ ions. The UV–Visible spectroscopic studies indicate that there are two characteristic absorptions of Co₃O₄ NPs indicating the ligand to metal charge transfer. The morphological analysis of Co₃O₄ NPs using field emission scanning microscope and high-resolution transmission electron microscopy, showed irregular shapes of different sizes with Co mostly at surface than the core. The magnetic data revealed the existence of antiferromagnetic nature co-hosting weak ferromagnetism. The detailed explanations of a straightforward and affordable method for creating spinel type Co₃O₄ and their structural and magnetic properties were explained.

We propose that the linear Dirac spectrum and the Rashba interaction, two important features of the topological insulators, have a common origin rooted on the well-known non-relativistic Schrödinger kinetic energy for fermions subject to the spin-momentum locking condition described here. This approach yields that the quasi-particles with linear Dirac spectrum are skyrmions, namely, three-dimensional vortices with topological charges surrounded by a residual local magnetic field. Within this framework, the spectrum of topological bilayers is obtained and shown for a small wave number to have two branches, one quadratic and the other linear but with twice the velocity of the single layer case.

Some theoretical studies using perturbation and tight-binding methods have tried to shed light on the magnetic behaviors of carbon-based nanostructures in the limit of wave vector (mathbf {q=0}). In a recent work, we studied a half-filled model of helical carbon chains to gain new insights for (mathbf {q ne 0}). Although in carbon the energy bands are usually derived from partially filled atomic p-shells, here we explore the hole contribution to these magnetic responses. We calculate the longitudinal spin susceptibility of an almost-filled tight-binding model of a helical chain for (mathbf {qne 0}). We find that when the Fermi level lies at the band edges, the system shows for positive chirality a divergent paramagnetic susceptibility. This result is in agreement with that previously reported for the macroscopic limit (mathbf {q=0}).

Magnetoresistance (MR), magnetoinductance (mi), and magnetoimpedance (MI) studies on the as-quenched and annealed Fe₇₂Si₁₀Cu₁Nb₂B₁₅, Co₇₂Ni₅Si₅Cu₁Nb₂B₁₅, and Co₇₇Si₅Cu₁Nb₂B₁₅ ribbons have been carried out in the present investigation. Structural studies indicate that all as-quenched samples are in the amorphous phase. The asymmetry in the MI, MR, and mi curves is noticed and is attributed to induced magnetocrystalline anisotropy and hysteretic magnetization. Among all three samples, the Co₇₇Si₅Cu₁Nb₂B₁₅ ribbons exhibit the highest magnetization and MI values. The development of a strong transverse magnetic anisotropy upon annealing has been observed in the Co₇₇Si₅Cu₁Nb₂B₁₅ ribbons, while such features are not observed in other cases. The present study shows that 5% Ni substitution in Co₇₇Si₅Cu₁Nb₂B₁₅ samples significantly reduces the transverse anisotropy, indicating that the transverse anisotropy can be tuned through Ni substitution.

By simulating the thermomagnetization of Ba(Fe_1-xSc_x)₁₂O₁₉ from approximately 100 to 750 K, the magnetocaloric effect (MCE) in Ba(Fe_1-xSc_x)₁₂O₁₉ samples is approximated. Intriguingly, the thermomagnetic property of the undoped sample BaFe₁₂O₁₉ is described as a conventional MCE for high temperatures. However, at doping levels x of 0.128, 0.153, and 0.189, respectively, the thermomagnetic property of Sc-doped samples is defined as an inverse MCE below temperatures of 163, 239, and 318 K. In contrast, thermomagnetic property of Ba(Fe_1-xSc_x)₁₂O₁₉ is described as conventional MCE above those temperatures. Additionally, Sc doping makes it possible for MCE in Ba(Fe_1-xSc_x)₁₂O₁₉ to be strongly tailored. This is helpful for operating a magnetic refrigerator (MR) which occurs in various temperature ranges and results in a higher working temperature range. A promising function for Ba(Fe_1-xSc_x)₁₂O₁₉ samples in MR at high-temperature applications in the automotive and food industries or aerospace.

We report the achievement of a high coercivity (Hc) value of 3 kOe for Mn₅₄Al₄₆ powders produced by high-energy ball milling without any heat treatment. The ferromagnetic α-Mn(Al) alloy powders were prepared with Mn (54 at%) and Al (46 at%) as the constituent metal elements. Analysis and discussion were held regarding the potential causes of the observed enhancement in the magnetic properties of the ball-milled powders in relation to their phase composition and microstructure. The process of milling causes partial solubilisation of Al atoms in the α-Mn phase and a change in the powder magnetic characteristics from paramagnetic to ferromagnetic. The existence of γ₂ and β phases was identified by XRD after long hours of the milling process. In addition, it was found that a longer milling time resulted in a smaller crystallite size, which also resulted in a decrease in magnetic saturation (Ms) but an increase in coercivity (H_C). Without applying any extra heat treatment, the Mn-Al powders milled for 6 h had optimum magnetic properties: Hc = 3.0 kOe, Mr = 0.05 emu/g, Ms = 0.19 emu/g, and (BH)max = 432 J/m³.

The scattering eigenstates of any Hamiltonian of electrons, coupled through a two-body force and moving on a one-dimensional lattice, are shown to be Bethe’s wave-functions. The energy of the groundstate is compared with values, obtained previously for the Hubbard Hamiltonian thanks to another Bethe’s wave-function-based procedure and within the framework of the correlated Fermi gas. The same analysis is applied to electrons, interacting on neighbouring sites. The significance of those various groundstates is assessed with help of thermodynamics.

The present study unveils the Decalepis hamiltonii leaves extract mediated biosynthesis of cobalt ferrite nanoparticles (DHLE.CoFe₂O₄ NPs) and its role on oxidative stress-induced inflammation, thrombosis and diabetes. DHLE.CoFe₂O₄ NPs were characterized using various techniques such as PXRD, FTIR, SEM, EDAX, HR-TEM and VSM. DHLE.CoFe₂O₄ NPs revealed irregular polygonal shapes with uneven distribution of particles with an average size of 19.13 nm. The DHLE.CoFe₂O₄ NPs displayed considerable anti-oxidant activity by scavenging DPPH free radical about 60.35% at 150 µg/mL concentration with an IC₅₀ value of 54.18 µg/mL. Similarly, DHLE.CoFe₂O₄ NPs reduced 744.06 µM ferric ions at the concentration of 150 µg/mL with an IC₅₀ value of 44.08 µg/mL. DHLE.CoFe₂O₄ NPs were non-toxic to RBCs and exhibited anti-oxidant property by regulating the stress markers such as LPO, PCC, TT, and anti-oxidant enzymes like CAT and SOD activities in NaNO₂-induced oxidative stress in RBCs model. Furthermore, DHLE.CoFe₂O₄ NPs were found to protect the RBCs’ membrane by inhibiting the hypo-tonicity and heat-induced hemolysis suggesting its anti-hemolytic activity. Furthermore, DHLE.CoFe₂O₄ NPs exhibited fair anti-inflammatory property that was tested using egg albumin, BSA denaturation and proteinase inhibition assays. In addition, DHLE.CoFe₂O₄ NPs inhibited α-amylase (46.45%) and α-glucosidase (48.66%) activity respectively and revealed its anti-diabetic property. Most importantly, DHLE.CoFe₂O₄ NPs showed anti-platelet activity by inhibiting both ADP and epinephrine-induced platelet aggregation with an inhibition percentage of 58.73 and 63.88, respectively. In conclusion, DHLE.CoFe₂O₄ NPs appear to be a good candidate in regulating oxidative stress-induced, inflammation, haemolysis, diabetes and thrombosis.