• S K Ghoshal

      Articles written in Bulletin of Materials Science

    • Kinetics of oxygen defect in YBCO

      S Dattagupta S K Ghoshal

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      Monte-Carlo simulations are described using the Kawasaki model of oxygen (dis)ordering in the basal plane of YBa2Cu3O7−δ(YBCO). In this model the presence or absence of an interstitial oxygen defect is mapped into a pseudo Ising spins=+1 or − 1. We study the rate law and the relaxation time of the order parameter and most importantly, the diffusion of oxygen in the basal plane across the structural phase transition in this system. In a separate investigation we have carried out numerical analysis of a mean-field dynamical model (with Kawasaki kinetics) to examine phase ordering dynamics and pattern formation, for δ=0.

    • Cu$^{2+}$ and Al$^{3+}$ co-substituted cobalt ferrite: structural analysis, morphology and magnetic properties

      SHADAB DABAGH ALI A ATI S K GHOSHAL SAMAD ZARE R M ROSNAN AHMED S JBARA ZULKAFLI OTHAMAN

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      Cu–Al substituted Co ferrite nanopowders, Co$_{1−x}$Cu$_x$Fe$_{2−x}$Al$_x$O$_4$ ($0.0 ≤ x ≤ 0.8$) were synthesized by the co-precipitation method. The effect of Cu–Al substitution on the structural and magnetic properties have been investigated. X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emissionscanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) are used for studying the effect of variation in the Cu–Al substitution and its impact on particle size, magnetic properties such as Ms and Hc. Cu–Alsubstitution occurs and produce a secondary phase, $\alpha$-Fe$_2$O$_3$. The crystallite size of the powder calcined at 800$^{\circ}$C was in the range of 19–26 nm. The lattice parameter decreases with increasing Cu–Al content. The nanostructural features were examined by FESEM images. Infrared absorption (IR) spectra shows two vibrational bands; at around 600 ($v_1$) and 400 cm$^{−1}$ ($v_2$). They are attributed to the tetrahedral and octahedral group complexes of the spinel lattice, respectively. It was found that the physical and magnetic properties have changed with Cu–Al contents. The saturation magnetization decreases with the increase in Cu–Al substitution. The reduction of coercive force, saturation magnetization and magnetic moments are may be due to dilution of the magnetic interaction.

    • Structural and physical properties of Sm$^{3+}$ doped magnesium zinc sulfophosphate glass

      F AHMADI R HUSSIN S K GHOSHAL

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      Samarium (Sm$^{3+}$) doped magnesium zinc sulfophosphate glass system of composition ($60–x$)P$_2$O$_5$–20MgO–20ZnSO$_4$–$x$Sm$_2$O$_3$ ($x = 0.0$, 0.5, 1.0, 1.5 and 2.0 mol%) were synthesized using melt-quenching technique. The structure and physical properties of prepared glass samples were characterized. The X-ray diffraction pattern verified their amorphous nature. The physical properties such as density, refractive index, molar volume, rare earth ion concentration, etc. were calculated. The decrease in the optical bandgap energy with increasing Sm$_2$O$_3$ contents was attributed to the alteration in the glass network structures. Fourier transformed infrared spectra and Raman analyses manifested the depolymerization ofZnSO$_4$ in the phosphate host matrix. The present findings may be beneficial for the advancement of functional glasses.

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