Nd Fe_（1-x）Ni_xO_3（0.1 ≤ x ≤ 0.7） orthoferrites are synthesized by solid state reaction method, and the structural properties of these materials are investigated by employing x-ray diffraction（XRD）, scanning e...Nd Fe_（1-x）Ni_xO_3（0.1 ≤ x ≤ 0.7） orthoferrites are synthesized by solid state reaction method, and the structural properties of these materials are investigated by employing x-ray diffraction（XRD）, scanning electron microscopy（SEM） and M o¨ssbauer spectroscopy. The orthorhombic structure is observed in all systems; however, with the increase in Ni doping,the increase in tolerance factor and the decrease in the cell volume are observed. Orthorhombic distortion decreases with Ni content increasing up to 50%, while above 50% Ni doping it increases. SEM examination indicates the increases in grain size and intermixing of grains with increase in Ni concentration. Comparison between bulk and theoretical densities shows that in each of all samples porosity is less than 2%. M？ssbauer spectroscopic investigations are performed to explain local structure, Fe oxidation states and collapse of the magnetic ordering. In these samples the Fe oxidation state remains＋3 and there is no considerable increase in hole states observed; however due to mismatch of the ionic radii between Fe^（3＋） and Ni^（3＋）, octahedral distortions, sagging and distribution of hyperfine parameters increase with increase in Ni concentration. The major factors behind the collapse of magnetic ordering in the Ni-doped systems are the weakening of the super-exchange interactions, decrease in the Neel temperature, increase in spin–spin relaxation frequency and high spin to low spin transition.展开更多
Optical emission spectroscopic measurement of trace rare gas is carried out to determine the density of nitrogen （N） atom, in a nitrogen plasma, as a function of filling pressure and RF power applied. 2% of argon, u...Optical emission spectroscopic measurement of trace rare gas is carried out to determine the density of nitrogen （N） atom, in a nitrogen plasma, as a function of filling pressure and RF power applied. 2% of argon, used as an actinometer, is mixed with nitrogen. In order to normalize the changes in the excitation cross section and electron energy distribution function at different operational conditions, the Ar-I emission line at 419.83 nm is used, which is of nearly the same excitation efficiency coefficient as that of the nitrogen emission line at 493.51 nm. It is observed that the emission intensity of the selected argon and atomic nitrogen lines increases with both pressure and RF power, as does the nitrogen atomic density.展开更多
Diffusion of Cu hexamer islands on Cu(111)and Ag(111)is studied using a molecular dynamics simulation technique with many-body potentials obtained from the embedded atom method.Simulations are carried out at temperatu...Diffusion of Cu hexamer islands on Cu(111)and Ag(111)is studied using a molecular dynamics simulation technique with many-body potentials obtained from the embedded atom method.Simulations are carried out at temperatures 300,500 and 700 K,showing that shape-changing multiple-atom processes are more helpful for the diffusion rather than concerted motion of islands.Arrhenius plots of the diffusion coefficients provide effective energy barrier values of 161.29±5 meV for Cu(111)and 179.34±5 meV for Ag(111)surfaces.At 700K,one pop-up atom among island atoms is observed with correlative changes in the position and shape of the lower-layer adatoms.展开更多
基金the Higher Education Commission (HEC) of Pakistan for the financial support through 5000 Indigenous Scholarship Scheme in Physical Sciences Batch-V for his Ph.D studiesPAEC for supporting this project
文摘Nd Fe_（1-x）Ni_xO_3（0.1 ≤ x ≤ 0.7） orthoferrites are synthesized by solid state reaction method, and the structural properties of these materials are investigated by employing x-ray diffraction（XRD）, scanning electron microscopy（SEM） and M o¨ssbauer spectroscopy. The orthorhombic structure is observed in all systems; however, with the increase in Ni doping,the increase in tolerance factor and the decrease in the cell volume are observed. Orthorhombic distortion decreases with Ni content increasing up to 50%, while above 50% Ni doping it increases. SEM examination indicates the increases in grain size and intermixing of grains with increase in Ni concentration. Comparison between bulk and theoretical densities shows that in each of all samples porosity is less than 2%. M？ssbauer spectroscopic investigations are performed to explain local structure, Fe oxidation states and collapse of the magnetic ordering. In these samples the Fe oxidation state remains＋3 and there is no considerable increase in hole states observed; however due to mismatch of the ionic radii between Fe^（3＋） and Ni^（3＋）, octahedral distortions, sagging and distribution of hyperfine parameters increase with increase in Ni concentration. The major factors behind the collapse of magnetic ordering in the Ni-doped systems are the weakening of the super-exchange interactions, decrease in the Neel temperature, increase in spin–spin relaxation frequency and high spin to low spin transition.
基金supported by the Higher Education Commission (HEC) of Pakistan. G. MURTAZA and S.S. HUSSAINthe financial support of HEC in their doctoral studies
文摘Optical emission spectroscopic measurement of trace rare gas is carried out to determine the density of nitrogen （N） atom, in a nitrogen plasma, as a function of filling pressure and RF power applied. 2% of argon, used as an actinometer, is mixed with nitrogen. In order to normalize the changes in the excitation cross section and electron energy distribution function at different operational conditions, the Ar-I emission line at 419.83 nm is used, which is of nearly the same excitation efficiency coefficient as that of the nitrogen emission line at 493.51 nm. It is observed that the emission intensity of the selected argon and atomic nitrogen lines increases with both pressure and RF power, as does the nitrogen atomic density.
文摘Diffusion of Cu hexamer islands on Cu(111)and Ag(111)is studied using a molecular dynamics simulation technique with many-body potentials obtained from the embedded atom method.Simulations are carried out at temperatures 300,500 and 700 K,showing that shape-changing multiple-atom processes are more helpful for the diffusion rather than concerted motion of islands.Arrhenius plots of the diffusion coefficients provide effective energy barrier values of 161.29±5 meV for Cu(111)and 179.34±5 meV for Ag(111)surfaces.At 700K,one pop-up atom among island atoms is observed with correlative changes in the position and shape of the lower-layer adatoms.
