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您的检索式：作者名="M.J.Akhtar"
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| 1 | Effects of Ni doping on the structural properties and collapse of magnetic ordering in NdFe_(1-x)Ni_xO_3(0.1 ≤x≤ 0.7) orthoferrites显示文摘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. | I.Ahmad M.J.Akhtar M.Siddique | 2016 | Chinese Physics B2016，25，2： | 0 |
| 2 | Interatomic Potentials for Some Binary Oxides显示文摘Using atomistic computer simulation methods we have derived a new set of interatomic potential parameters for some binary oxides, comprising divalent transition elements (rock-salt structured) and tetravalent metals. Computational techniques based on the minimization of the crystal energy with respect to atomic coordinates have been employed. Crystal properties were calculated and compared with the experimental data to check the reliability of our potential models. Intrinsic (Schottky and Frenkel) defect energies were also calculated and compared with previous studies. There is a good agreement between these calculations, which shows that the new potential parameters are reliable and can be used with confidence for future investigations. | M.Nadeem, M.J.Akhtar, R.Shaheen and M.N.Haque Nuclear Physics Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad, Pakistan A.Y.Khan Department of Chemistry, Quaid-i-Azam University, Islamabad, | 2001 | Journal of Materials Science & Technology2001，17，6： | 0 |
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