Journal of Superconductivity and Novel Magnetism最新文献

We investigate plasmon properties in a double-layer graphene structure under the effects of an in-plane external magnetic field within the zero-temperature random-phase approximation. Numerical calculations demonstrate that two plasmon modes exist in the system, corresponding to in-phase and out-of-phase oscillations of charges. The spin polarization number P affects the optical and acoustic plasmon modes and their decay rate differently. As the polarization number increases, the frequency of the acoustic mode slightly decreases while that of the optical mode significantly increases. Besides, the existence of an external magnetic field expands the single-particle-excitation area of the system; therefore, plasmon modes become damped at a smaller wave vector, compared to those in the case of unpolarized systems. The separation between two layers increases (decreases) the plasmon frequency of the acoustic (optical) mode. Finally, we found that background dielectric inhomogeneity decreases the energy and decay rate of plasmon modes of the spin-polarized system.

Breast cancer is one of the deadliest cancers for women, so cell labeling and therapy of breast cancer become imperative. In this work, dextran- and carboxymethyl dextran–coated Fe₃O₄ nanoparticles (Fe₃O₄@DEX and Fe₃O₄@CMD) were well synthesized through the co-precipitation method. The dextran and carboxymethyl dextran coating reduces the average particle size of Fe₃O₄ nanoparticles from 10.9 to 4.0–5.5 nm, and the coated samples exhibit average hydrodynamic diameters ranging from 31 to 110 nm. The coating promotes the dispersibility of nanoparticles. Saturation magnetization is reduced from 60.3 to 5.6–7.1 emu/g in the coated MNPs due to the large weight ratio of the coating layer and the decrease in particle size. Hemolysis and cytotoxicity assay results indicate the excellent biocompatibility of Fe₃O₄ nanoparticles. The cellular uptake assay confirms that both dextran- and carboxymethyl dextran–coated Fe₃O₄ nanoparticles are easily taken in by breast cancer cells. Comprehensively considering dispersion, biocompatibility, and cellular uptake, the Fe₃O₄@CMD is more suitable for application in the bio-labeling of breast cancer cells. The SAR values of the Fe₃O₄@DEX and Fe₃O₄@CMD range from 19.2 to 30.7 W/g. The SAR value is mainly influenced by the hydrodynamic diameter in the coated samples. The Fe₃O₄@CMD20 shows the maximum SAR value of 30.7 W/g and has potential application in magnetic hyperthermia therapy.

The method of linearized full-potential augmented plane waves based on density functional theory (DFT) is employed to investigate the structural, elastic, magnetic electronic, and thermoelectric properties of the cerium-based half-Heusler alloy FeCeSi. The exchange correlation functional is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE) and the Tran-Blaha-modified Beck-Johnson (TB-mBJ) as implemented in the Wien2k package. According to our results, we have discovered that the material studied is mechanically stable, which means that this compound can be synthesized experimentally. Furthermore, FeCeSi exhibits a half-metallic behavior obeying the Slater-Pauling rule with an integer magnetic moment of 2 μB. The electronic band structures and density of states confirm the half-metallic character with an indirect band gap equals to 0.51 eV and 0.59 eV for GGA-PBE and TB-mBJ approximation, respectively. For the study of the thermoelectric parameters, such as Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (κ), and figure of merit (ZT), the Boltzmann transport equations within the framework of DFT have been used. Significant values for the figure of merit and Seebeck coefficient indicate promising candidate for useful thermoelectric applications for FeCeSi alloy. So far, no experimental or theoretical investigations have been carried out on the half-Heusler alloy FeCeSi. Accordingly, our theoretical results concerning structural, elastic, electronic, magnetic, and thermoelectric properties will probably be confirmed by experimental investigations.

A high sensitivity photonic crystal fiber (PCF) magnetic field sensor based on Sagnac interferometer is proposed. All the air holes of the PCF are completely filled with the magnetic fluid (MF), which is a magnetic liquid material. The sensing performance of PCF is simulated and analyzed by using finite element method (FEM). It is found that the effects of wavelength λ, phase birefringence B(λ,H), and group birefringence B_g(λ,H) on the sensitivity are very significant. The two dip points in this spectrum show a red shift and a blue shift as the refractive index of the magnetic fluid increases, respectively. This magnetic field sensor obtains the average sensitivity of 889.5 pm/Oe (111,684.9 nm/RIU) and −994.3 pm/Oe (−124,839.5 nm/RIU) in the range from 90 to 240 Oe.

Structural, magnetic, and dielectric properties of (x)SrFe₁₂O₁₉-(1-(x))Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ multiferroic composite prepared by sintering the composite mixture of sol-gel synthesized SrFe₁₂O₁₉ (SrF) and Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ (BCTZ) are reported. Structural parameters (lattice parameter, bond length, and lattice strain) of parent phases in their pure and composite forms are correlated to indicate the lattice interaction between the two phases. The magnetic moment per gram of SrF (({M}_{SrF})) in the composite is higher than that in the SrF, related to the changes in the Fe-O-Fe bond angles. The room temperature dielectric response of the composites in the 100 Hz–10 MHz frequency range is modeled by the Cole–Cole relaxation and Jonscher power law equations to mark the different contributions (ferroelectric dipoles, charge carriers).

Impact of shot peening on SS347 tube has been investigated using MagStrics, a magnetostrictive sensing (MsS) device comprising of rapidly quenched ribbon as sensor element. Two tubes of SS347 have been considered in pre- and post-shot peened state. Annealed ribbon as sensor element showed enhanced MsS signal. Using the annealed ribbon as sensor element, the MsS signal amplitude in shot peened tube was found to be distinctly different from un-peened sample. This was associated to magnetic phase evolutions in the pipe internal surface due to shot peening. Such phenomena have been endorsed through SEM–EDX compositional analysis and correlated through simulations using COMSOL Multiphysics.

Nowadays, the concept of non-trivial topological protection and the nanoscale size of nanomagnetic particles constitute a major area of research. Due to topological protection stability, nanoscale size, and the requirement of low spin current density for motion, skyrmions have attracted great attention in next-generation spintronic devices as robust information carriers. We study the motion of an isolated magnetic skyrmion with induced interfacial Dzyaloshinskii-Moriya interaction (iDMI) instigated by spin waves and driven by spin current with variation in different parameters in a nanotrack of finite length using micromagnetic simulations. It is found that the magnetic skyrmion moves in the same direction as the direction of propagation of the spin waves. The skyrmion initially experiences an acceleration in its motion; thereafter, the velocity decreases exponentially. The motion of the magnetic skyrmion initiates as the momentum of the spin wave gets transferred to it. The motion of the magnetic skyrmion is found to be significantly dependent on the variation of parameters like frequency and amplitude of the incident spin waves, as well as the damping parameter and the strength of the applied spin-polarized current. The results obtained in this work could become useful to design skyrmion-based spintronic information-carrying and storage devices.

Conventional solid-state reaction method has been cautiously employed to prepare the Ba_0.75Sr_0.25Ti_1−xMn_xO₃ ceramic where Sr was firmly doped at the Ba site and Mn was doped with different densities at the Ti site. Since the performance of materials varies with frequency, electric field, and temperature, we have elucidated the various features of the synthesized samples for the sake of scientific benefit in the fields of microelectronics, telecommunications, and spintronics. Structural and morphological features of the ready samples were examined by X-ray diffraction and scanning electron microscopy (SEM). The crystal's tetragonal behavior was verified by XRD analysis, and with the increment of Mn content, the volume of the unit cell is little changed. It is clear from the SEM images that the grain size of the prepared samples increases with Mn doping. The dielectric properties of Ba_0.75Sr_0.25Ti_1−xMn_xO₃ were measured by dielectric constant and AC conductivity in a wide range of frequency from 1 kHz to 10 MHz. This result also explores that the dielectric constant rises with the concentration of Mn, most significantly for the 20% Mn substitution with Ti. We also found from the experimental result that the dielectric constant is high in the frequency range of 1–10 kHz. The magnetic permeability of the prepared sample increased with 10% and 20% of Mn replacement. Ferromagnetic features with a weak coercive field and the increased ferromagnetic order with rising Mn concentrations of the prepared samples were confirmed by VSM data analysis. The developed multiferroic materials can be employed in future spintronic devices like spin transistors, sensors, spin diodes, and memory devices.

In this paper, we report a systematic study on effect of film thickness and substrate temperature on structural and magnetic behaviour of Fe-Ga films with Cu buffer layer, deposited on Si and Si/SiO₂ substrates at room and high substrate temperatures. Grazing incidence X-ray diffraction studies reveal that all the films are crystalline with disordered alpha-Fe phase, which is BCC A2 phase. At 300 °C of substrate temperature, films deposited on Si/SiO₂ substrate found to nucleate L1₂ phase from matrix of A2 phase, which is not seen in Si based films. Irrespective of substrate material, Fe-Ga films found to exist in dual phases at 500 °C substrate temperature. Lattice strains of the films were calculated from X-ray diffraction patterns, using Williamson-Hall method. From X- ray reflectivity analysis of all the films, film density, thickness and roughness of Fe-Ga layer and buffer layer were obtained after fitting the reflectivity data. Presence of an oxide layer is also evident from reflectivity fitting analysis. From magnetization studies it is clear that, all the films exhibited strong in-plane anisotropy. Saturation magnetization of films was found to vary with change in film density and oxide layer thickness of films. Saturation magnetization of films deposited on Si substrates found to decrease with decrease in film density. Coercivity of films found to vary with change in crystallite size, interface roughness and lattice strain of films. Films deposited on Si substrates are sensitive to strain with change in film thickness and films deposited on Si/SiO₂ substrates are sensitive to strain with change in deposition temperature. Coercivity in films found to decrease with decrease in film roughness, increase in crystallite size and lowering the tensile lattice strain.

In this paper, we have investigated the magnetic and magnetocaloric characteristics of a La₂MnNiO₆ composite, in conjunction with La₂MnCoO₆. This composite consists of two phases of double perovskite materials. Employing the mean-field approximation, we successfully modeled how magnetization and the change in magnetic entropy vary with temperature under different magnetic fields in our samples. This phenomenological model helped us also plot the maximum magnetic entropy change (-ΔS_M)_max, full width at half-maximum δT_FWHM, and relative cooling power (RCP). Our analysis has revealed an optimal plateau-type magnetocaloric effect near room temperature, corresponding to a specific composition x between 0.2 and 0.5. Ultimately, this theoretical model lets us predict the magnetic and magnetocaloric behavior of composite materials, providing a foundation for future studies.