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    Crystallization process, microstructure, thermal behavior, and magnetic properties of melt‑spun Fe86Cr6P6C2 ribbons
    (Applied Physics A, 2023-04-14) Abadlia Lakhdar; Daoudi Ibrahim; Alleg Safia
    Abstract The crystallization process, microstructure, thermal stability, and magnetic properties of Fe86Cr6P6C2 amorphous ribbons were studied by X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, differential scanning calorimetry, and vibration sample magnetometry. The crystallization process occurs in three stages where nanocrystalline α-Fe solid solution, Fe3P phosphide, θ-Fe3C and ε-Fe3C carbides are formed. The crystallite size increases with increasing annealing temperature and remains at the nanometer scale (20–88 nm). The microstructure of the annealed ribbons consists of lamella, fine platelets, alternate planes of ferrite and cementite, and grains with different shapes and sizes. The activation energies (499, 386, and 369 kJ/mol) are determined by Kissinger method. The melt-spun ribbons exhibit a low coercivity of 16.598 Oe and a high saturation magnetization of 0.635 emu compared to the annealed ones. The saturation magnetization decreases to a minimum value for the annealed ribbons at 758 K and then increases with increasing the annealing temperature. The Curie temperature increases from 447.4 K for the melt-spun ribbons to 638 K for the fully crystallized ribbons due to the development of the α-Fe phase.
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    Chirped localized pulses in a highly nonlinear optical fiber with quintic non-kerr nonlinearities
    (Results in Physics, 2022-10-07) Faissal Mansouri; Sassi Aouadi; Houria Triki; Yunzhou Sun; Yakup Yıldırım; Anjan Biswas; Hashim M. Alshehri; Qin Zhou
    We study the existence and propagation properties of chirped localized pulses in a highly nonlinear fiber medium exhibiting self-steepening, self-frequency shift, and quintic non-Kerr nonlinearities. Pulse evolution in such fiber system is governed by a higher-order nonlinear Schrödinger equation incorporating the derivative Kerr and non-Kerr nonlinear terms. We show that bright, dark and kink type solitary waves exist in the presence of all physical processes. A special ansatz is introduced to analyze the existence of solitary waves on a continuous-wave background in the optical fiber medium. It is shown that the obtained localized pulses exhibit a nonlinear chirp which has a quadratic dependence on light intensity. We also find that the magnitude of the associated frequency chirp can be controlled effectively by varying the parameters of self steepening, self-frequency shift, and derivative non-Kerr nonlinearity effects. The restrictions on the optical fiber parameters are also extracted for the existence of these nonlinearly chirped solitary waves. Results in this study may be useful for experimental realization of shape-preserved pulses in optical fibers and further understanding of their optical transmission properties.