Journal of Superconductivity and Novel Magnetism最新文献

Films with varying compositions of Zn_1-xFe_xO (0 ≤ x ≤ 0.10) were produced using the sol–gel technique. The structural, optical, and magnetic studies were examined via “X-ray diffraction,” “EDX,” “UV–Vis spectrophotometer,” and “vibrating magnetometer.” The X-ray analysis data shows that all the films under examination have a hexagonal polycrystalline structure. As well, the crystallite size, D, reduced from 16.7 to 12.5 nm as the Fe ratio rose. The current findings show that the band gap, E_g^opt, is decreasing from 3.389 to 3.036 eV, suggesting the sp-d exchange that occurs between the s-p electrons of the valence and conduction bands and the d-electrons associated with the doped Fe³⁺ ions. Additionally, the refractive index, n, extinction coefficient, k_ex, and coefficient of Verdet, Vλ, as well the sheet resistance, R_s, and the figure of merit, φ, are estimated as a function of the doped Fe³⁺ ions ratio. Furthermore, the dispersion energy, E_d, increased from 11.476 to 11.906 eV, while the single oscillator energy, E_o, decreased from 6.72 to 6.063 eV. These results evidence that the incorporation of Fe into the ZnO lattice leads to the tunability of the optical properties. Finally, the measurements of magnetization exhibit a hysteresis loop in Fe-doped ZnO nanofilms, confirming the presence of room-temperature ferromagnetism. Making the Fe-doped ZnO films is suitable for use in optoelectronic and spintronic device applications.

A comparative specific heat (C(_{P})) study of GdPdAl and TbPdAl compounds crystallizing in hexagonal ZrNiAl-type crystal-structure (space group P(bar{6})2 m) is presented. Consistent with earlier reports both the compounds show the signature of two magnetic transitions in magnetization data. The magnitude of the jump in C(_{P}) at the high-temperature transition at T(_{N1}) ((sim )47 K ) in GdPdAl indicates ordering into an amplitude-modulated magnetic structure. The analysis of magnetic entropy change (S(_{4f})) showed that about one-half of total S(_{4f}) occurs below low temperature transition at T(_{N2}). This is in contrast to that seen in TbPdAl, where only one-third of the entropy of transition occurs below T(_{N2}). For both the compounds S(_{4f}) tends to saturate to about 84% (for T > T(_{N1})) of that expected for complete ordering of the rare earth moments, indicating incomplete removal of geometrical frustration.

Domain wall (DW)-based devices are attractive for mimicking synaptic behavior, which is fundamental to the realization of neuromorphic computing architecture. Unlike digital electronic devices, it requires analog switching. In this work, we demonstrate the multistate analog switching in a rectangular nanowire with multiple anti-dots using micromagnetic simulations. Anti-dots act as pinning sites for the DW motion during magnetization reversal. The vortex DWs nucleated during the reversal undergo transformation to transverse configuration due to the pinning at the anti-dots. The depinning of the transverse DW takes place in multiple steps. We have also observed the generation of multiple 360° DWs in this structure. The transverse DW breaks into smaller DWs during depinning, leading to stable magnetization states. The number of states achieved directly depends on the number of anti-dots introduced in the nanowire. By introducing six anti-dots, ten stable magnetization states are achieved. The change in demagnetization energy as a function of configuration, shape, and size of the DW is responsible for the observed multistate analog behavior.

Crystal structure, opto-electronic, magnetic, and thermoelectric properties of quadruple perovskites ACu₃Ti₂Ru₂O₁₂ (A = Ca, Sr, and Ba) are explored by the utilization of generalized gradient approximation (GGA) and GGA with Hubbard U in the framework of density functional theory (DFT). The optimized crystal structures and geometrical appearance are found compatible with the experiments. Cohesive energies (− 35.92 to − 39.41 Ry) and enthalpy of formation (− 1.79 to − 1.97 Ry) describe the stability of these compounds. Electrical resistivity and AFM phase profiles of electronic bands of these perovskites indicate that they are semiconductors with band gap ranging from 0.50 to 0.17 eV accordingly. In these compounds, the bandgap arise between the Ti and Ru d states electron and are direct band gap materials at R symmetry. They are active in the infrared part of the electromagnetic spectrum, according to their optical characteristics; this makes them shields for UV radiation and potential candidate for security monitoring devices. Thermoelectric properties of these compounds demonstrate that they are suitable candidate for thermoelectric generation. All of these perovskites are antiferromagnetic (AFM) which can be evident from their magnetic susceptibility and stable magnetic phase energies. As these perovskites are AFM semiconductor, due to this property, these perovskites could be used in magnetic cloaking and high-speed switching devices.

Soft magnetic films play a crucial role in numerous technological applications, such as magnetoelectronics, telecommunications, and magnetic recording, and the tuning of properties to obtain high-efficiency demands searching new materials and controlling thickness and compositions. In this regard, we report a systematic investigation of structural, morphological, electrical resistivity, and temperature-dependent magnetic properties of single-layer amorphous Fe₇₀Co₁₅Zr₇B₅Cu₃ HITPERM (t = 5–100 nm) films deposited on a low-cost thermally oxidized Si substrate. Structural studies (XRD and TEM) reveal an amorphous nature in all as-deposited films. Surface morphology shows that the average roughness increases with increasing t up to 50 nm and then decreases at higher thicknesses. The electrical resistivity decreases rapidly as t increases from 5 to 10 nm and then is invariant for films with t ≥ 30 nm. Interestingly, the variation of resistivity follows the Boltzmann fitting. These films exhibit tunable magnetic properties between soft (t < 20 nm) and semi-hard (20 nm < t < 70 nm) properties with rectangular-type magnetic hysteresis loops having ~ 100% remanence ratios (M_r/M_s), low coercivity (H_c < 2.5 kA/m), and low saturation magnetic field (H_s < 3 kA/m) for t ≤ 70 nm. Transcritical hysteresis loop with a large H_c > 6.7 kA/m, high H_s > 26.5 kA/m, and reduced M_r/M_s ~ 55% is observed for t = 100 nm film. High-temperature thermomagnetization curves display two magnetic phase transitions (T_C) corresponding ferromagnetic state to a paramagnetic state of the amorphous phase (at 820 K during warming) and nanocrystalline phase (at 1003 K during cooling). The observed results of HITPERM films with large T_C naturally make it a potential choice for applications not only in magnetoelectronics at room temperature but also for aircraft power devices at higher temperatures.

In this study, we explored the structural, magnetic, and magnetocaloric properties of Fe(_{3})Al off-stoichiometric samples prepared using the vacuum arc melting technique. X-ray diffraction studies confirmed the cubic (D0_{3})-type structure in these samples. M(H) curve revealed soft ferromagnetic behavior with low coercivity and good magnetic saturation. The magnetization vs temperature studies demonstrated a decrease in the Curie temperature from 906 to 620 K with an increase in Al composition. Notably, the Fe(_{73})Al(_{27}) sample exhibited a substantial magnetic entropy change ((varDelta )S(_{M}) = (-)5.5 J kg(^{-1}) K(^{-1})) and a high relative cooling power (RCP = 307 J kg(^{-1})) at 906 K. Further, the thermo-magnetic studies of these off-stoichiometric alloys have provided an insight into the Curie temperature dependency over the Al composition. The increase in the Al composition has shifted the Curie temperature towards the lower temperatures while changing the underlying crystallographic structure from B2 to (D0_{3}).

Ce-substituted M-type Sr_1–xCe_xFe₁₂O₁₉ (x = 0.00–0.08) ferrites were successfully synthesized via the ball milling method, and the sintering temperature at 1200 °C for 2 h. The synthesized materials were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The elemental makeup of the samples was characterized by energy-dispersive spectrometry (EDS). The XRD results showed the crystal structure and purity of the samples. The FTIR spectroscopy indicated tetrahedral and octahedral tensile vibrations of M-type strontium ferrite at two characteristic peak bands of 554 and 454 cm⁻¹. The FESEM showed that Ce doping resulted in fine grains. The EDS indicated that Ce content increased with decreasing Sr concentration but that the concentrations of other elements remained basically unchanged. The mass ratio of Sr:Fe is calculated from EDS results and the measured Sr:Fe mass ratio is quite close to the mass ratio calculated from the reactants used to synthesize each sample. The VSM showed that at a Ce doping of x = 0.02, the coercivity of the samples reached the maximum, and the coercivity values and the saturation magnetization were 3878.25 Oe and 73.625 emu/g, respectively. And such high thermal stability further determines that Ce-substituted strontium ferrites have infinite potential in application fields (T = 450.2 °C).

We studied the dynamical spin susceptibility within the Hubbard model for hole-doped cuprates using cluster perturbation-based methods. Together with the one-electron spectral function, the two-particle response for 3 × 3 and 4 × 4 clusters are calculated and compared to each other. The results obtained are in qualitative agreement with the resonant inelastic neutron scattering and quantum Monte Carlo data.