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Register a new userRadiation Shielding Properties of $Nd_{0.6}Sr_{0.4}Mn_{1-y}Ni_{y}O_{3}$ Substitute with Different Concentrations of Nickle
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In this work, we investigate the effect of Ni concentration on several shielding properties of $Nd_{0.6}Sr_{0.4}Mn_{1-y}Ni_{y}O_{3}$ (0.00 $leq$ y $leq$ 0.20) perovskite ceramic for possible use as radiation shielding materials. X-ray diffraction (XRD) analysis revealed that these ceramics have the orthorhombic structure with group space Pnma over a wide range of Ni-substitutions. Moreover, the analysis showed a nearly linear decrease in the lattice parameters and the unit cell volume (V) causing a gradual increase in the packing density with increasing Ni concentration. The shielding features for photons, neutrons, and protons of all ceramic samples were assessed. The mass attenuation coefficient (MAC) was computed at 0.1, 0.6, 1.25, 5 and 15 MeV by utilizing (MCNP) (version 5.0); the results were compared with the corresponding values obtained using Phy-X and XCOM program. The results obtained showed slight enhancement with increasing Ni contents. The substitution of Ni leads to progressive enhancement in effective removal cross-section of fast neutron (${Sigma}$R) values. Whereas the values of Mass Stopping Power (MSP) and projected range for the protons showed a gradual reduction with increasing Ni concentration. These findings suggest that the current ceramic samples can be useful as radiation shielding materials.
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We investigate the effect of Ni${text -}$substitution on the crystalline structure and the critical behavior of $Nd_{0.6}Sr_{0.4}Mn_{1-x}Ni_{x}O_{3}$ (0.00 $leq$ x $leq$ 0.20) perovskite. X${text -}$ray diffraction patterns revealed that the major phase in all samples is the orthorhombic structure with space group $textit{Pnma}$. Rietveld refinement revealed a linear reduction in the lattice parameters along with monotonic reduction in the O2${text -}$Mn${text -}$O2 angel with increasing Ni concentration. The modified Arrott plots and the Kouvel${text -}$Fisher method have been used to analyze the magnetization isotherms near the paramagnetic to ferromagnetic (PM${text -}$FM) phase transition. The obtained critical exponents ($beta$, $gamma$ and $delta$) revealed that the Ni${text -}$free sample is consistent with 3D${text -}$Heisenberg like behavior. However, upon Ni${text -}$substitution, the critical exponents exhibit a mean field like behavior. The reliability of the obtained critical exponent ($beta$, $gamma$ and $delta$) values have been confirmed by the universal scaling behavior of the isothermal magnetization near the transition temperature.
We present the electronic structure of Sr_{1-(x+y)}La_{x+y}Ti_{1-x}Cr_{x}O_{3} investigated by high-resolution photoemission spectroscopy. In the vicinity of Fermi level, it was found that the electronic structure were composed of a Cr 3d local state with the t_{2g}^{3} configuration and a Ti 3d itinerant state. The energy levels of these Cr and Ti 3d states are well interpreted by the difference of the charge-transfer energy of both ions. The spectral weight of the Cr 3d state is completely proportional to the spin concentration x irrespective of the carrier concentration y, indicating that the spin density can be controlled by x as desired. In contrast, the spectral weight of the Ti 3d state is not proportional to y, depending on the amount of Cr doping.
Electronic structures of very dilute Cr- or Ru-doped Nd_{1/2}A_{1/2}MnO_{3} (NAMO; A=Ca, Sr) manganites have been investigated using the Mn and Cr 2p -> 3d resonant photoemission spectroscopy (PES). All the Cr- and Ru-doped NAMO systems exhibit the clear metallic Fermi edges in the Mn e_g spectra near E_F, consistent with their metallic ground states. The Cr 3d states with t^3_{2g} configuration are at ~ 1.3 eV below E_F, and the Cr e_{g} states do not participate in the formation of the band near E_F. Cr- and Ru-induced ferromagnetism and insulator-to-metal transitions can be understood with their measured electronic structures.
It has been clarified that bulk superconductivity in Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ can be induced by annealing in an appropriate atmosphere to remove the harmful effects of excess iron. In order to clarify the details of the annealing process, we studied the changes in the physical properties and reaction products of Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ annealed in pnictogen (P, As, Sb) atmospheres. Crystals annealed in a pnictogen atmosphere show bulk superconductivity and the values of $T_{c}$ and $J_{c}$ are about $14~$K and 2-4 $times 10{^5}~$A/cm$^2$ ($2~$K, self-field), respectively. It is also found that the reaction rate increases with the increase in the saturated vapor pressure of the pnictogen. Unexpectedly, the reaction products of Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ after annealing in a P atmosphere mainly consist of FeTe$_2$. In addition, the amount of P required to obtain the optimal $T_{c}$ is much smaller than the amount of excess iron, which is similar to the case of oxygen annealing. P, oxygen, and to some extent As could serve as catalysts to form FeTe$_2$ to remove excess iron.
We report a detailed study of the electric transport and magnetic properties of the LaNdCaMnO manganite system. Substitution of LaIII by smaller NdIII ions, reduces the mean ionic radius of the A site ion. We have studied samples in the entire range between rich La and rich Nd compounds. Results of DC magnetization and resistivity show that doping destabilize the FM character of the pure La compound and triggers the formation of a phase separated state at intermediate doping. We have also found evidence of a dynamical behaviour within the phase separated state. A phase diagram is constructed, summarizing the effect of chemical substitution on the system.
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