Papers by Author: Asghari Maqsood

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Authors: Ghulam Shabbir, Asghari Maqsood, Izhar-ul-Haq
Abstract: Micro-Brillouin light scattering experiments were performed on flux grown D-type (monoclinic, P21/c) Ho2Si2O7 single crystal from room temperature to 850 K. Both the hypersonic velocity (VLA) and related elastic constant (c33) of the longitudinal acoustic phonons propagating along 001-direction showed a small dispersion at T565 K whereas the same could not be observed clearly in attenuation/damping. The overall temperature dependent behavior of elastic constant and hypersonic velocity was attributed to the lattice anharmonicity of the crystal in the investigated temperature range.
Authors: Shahid Ameer, Asghari Maqsood
Abstract: The compound Dy2Si2O7 exists in two polymorphs, the low temperature triclinic phase (type B) and a high temperature orthorhombic phase (type E).The dc and ac electrical conductivities of E-Dy2Si2O7 are measured in the temperature range 290-510 K and frequency range 1 kHz to 1 MHz . The dc electrical transport data are analyzed according to Motts variable-range hopping model. The disorder parameter (To) and density of states at fermi level are obtained. The ac conductivity σac (ω) is obtained through the dielectric parameters. The ac conductivity can be expressed as σac (ω) =B ω s , where s is slope and it decreases with increase in temperature. The conduction mechanism in the compound is discussed in low and high temperature regions in the light of theoretical models.
Authors: Ahmad Faraz, Asghari Maqsood, Nasir M. Ahmad, Fazal Ur-Rehman, Shahid Ameer
Abstract: Spinel Nanoferrites of Composition Mg0.50Cu0.5-XNixFe2O4 (0.00≤x≤0.50) Were Synthesized by Chemical Co-Precipitation Method. the Structural, Morphological and Magnetically Changes due to Varying Concentrations of Metal Ions of Cu and Ni in the Prepared Nanoferrites Were Studied. XRD Confirmed the Formation of Single Phase Spinel Ferrite with Crystalline Sizes in between 16-29 Nm, and the Lattice Parameter (a) Found to Decreases with Increase of Ni Concentration. Electrical Resistivity of the Prepared Nanoferrites with Varying Nickel and Copper Concentrations X Observed to Follow Arrhenius Relation and Also Exhibited the Semiconductor Behavior. the Magnetic Hysteresis Curves Clearly Indicate the Soft Nature of the Prepared Samples. Saturation Magnetization (Ms) Increases with Ni Content. This Effect Is Related to the Magnetic Moments of Ni+2 Ions. the Y-K Angles Increase with Increasing Ni Content, and Suggest a Non Collinearity Néel Type of Ordering of the Y-K Type. the Increase in the Y-K Angles Also Suggests the Increase in Triangular Spin Arrangements on B Sites, which Subsequently Lead to Increment in A-B Interactions.
Authors: M. Anis-ur-Rehman, M.A. Malik, S. Nasir, M. Mubeen, K. Khan, Asghari Maqsood
Abstract: The nanocrystalline Mg-Zn ferrites having general formula Mg1-xZnxFe2O4 (x=0, 0.1, 0.2, 0.3, 0.4, 0. 5) were prepared by WOWS sol-gel route. All prepared samples were sintered at 700°C for 2 h. X-ray powder diffraction (XRD) technique was used to investigate structural properties of the samples. The crystal structure was found to be spinel. The crystallite size, lattice parameters and porosity of samples were calculated by XRD data analysis as function of zinc concentration. The crystallite size for each sample was calculated using the Scherrer formula considering the most intense (3 1 1) peak and the range obtained was 34-68 nm. The dielectric constant (ε), dielectric loss tangent () and AC electrical conductivity of nanocrystalline Mg-Zn ferrites are investigated as a function of frequency. The dielectric constant (ε), dielectric loss tangent () increased with increase of Zn concentration. All the electrical properties are explained in accordance with MaxwellWagner model and Koops phenomenological theory.
Authors: M. Anis-ur-Rehman, Mughal Zeb-un-Nisa, Mariam Ansari, Asghari Maqsood
Abstract: Manganese doped cobalt nano ferrites were synthesized by co-precipitation method having general formula Co1-xMnxFe2O4 (x =0.0-1.0). These materials are studied to analyze the structural effects on the associated materials properties. The prepared samples were heat treated at 7500 C for two hours. Sintering effect on the structural properties was investigated. The lattice constants of samples were measured from X-rays diffraction data. The (311) peak was used to find crystallites size by the Scherrer formula. Structural morphology was observed by scanning electron microscopy. Variation with temperature in electrical resistivity (DC) and drift mobility were also investigated. The variations with frequency and composition in AC electrical properties of prepared samples were determined. The structural and electrical properties demonstrated firm association. Saturation magnetization, coercivity and remanence of the samples were discussed with the help of sharing of cations within crystals.
Authors: Shahid Ameer, Ahmad Faraz, Asghari Maqsood, Nasir M. Ahmad
Abstract: The Polymorphic Er2Si2O7 Is Synthesized by Solid State Double Sintering Method. Structural and Morphological Characterizations Have Been Performed Using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The Electrical Characterization Has Been Performed by Two Probe Method as a Function of Temperature. the Dielectric Spectroscopic Measurements of Polymorphic Er2Si2O7 Are Performed in the Temperature Range 300-555 K and Frequency Range 3 kHz to 1 MHz. the dc Electrical Transport Data Are Analyzed According to Mott’s Variable-Range Hopping. The ac Conductivity σac(ω) Is Obtained through the Dielectric Spectroscopic Measurements. the ac Conductivity Obeys Power Law which Can Be Expressed as σac (ω) = B ωs, where S Is Slope and it Determines the ac Electrical Transport Phenomenon. the ac Electrical Transport Data and its Variation with Temperature in this Rare Earth Formulation Are Well Discussed. the Magnetic Behavior of Synthesized Material Is Analyzed and Confirmed that Material Have Non-Magnetic Behavior with Coercivity (Hc) 842 Oe. while the Values of Magnetic Saturation (MS) and Remanace (Mr) Were Found in Range 3.90emu/g and 1.07emu/g.
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