Aditya Sharma

Punjab Technical University, Mba, Department Member

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Swift heavy ion irradiation induced nanoparticle formation in CeO 2 thin films

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2011

In this paper we investigated structural, electronic, and magnetic properties of 3d ͑light͒ trans... more In this paper we investigated structural, electronic, and magnetic properties of 3d ͑light͒ transition metal atomic chains using first-principles pseudopotential plane-wave calculations. Infinite periodic linear, dimerized linear, and planar zigzag chain structures, as well as their short segments consisting of finite number of atoms have been considered. Like Cu, the periodic, linear chains of Mn, Co, and Ni correspond to a local shallow minimum. However, for most of the infinite periodic chains, neither linear nor dimerized linear structures are favored; to lower their energy the chains undergo a structural transformation to form planar zigzag and dimerized zigzag geometries. Dimerization in both infinite and finite chains is much stronger than the usual Peierls distortion and appears to depend on the number of 3d electrons. As a result of dimerization, a significant energy lowering occurs which, in turn, influences the stability and physical properties. Metallic linear chain of vanadium becomes half-metallic upon dimerization. Infinite linear chain of scandium also becomes half-metallic upon transformation to the zigzag structure. An interplay between the magnetic ground state and the atomic as well as the electronic structure of the chain has been revealed. The end effects influence the geometry, the energetics, and the magnetic ground state of the finite chains. Structure optimization performed using noncollinear approximation indicates significant differences from the collinear approximation. Variation of the cohesive energy of infinite-and finite-size chains with respect to the number of 3d electrons is found to mimic the well-known bulk behavior. The spin-orbit coupling of finite chains is found to be negligibly small.

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Structural and magnetic properties of Ce1−xCoxO2 (0 ⩽ x ⩽ 0.1) nanocrystalline powders

Physica Scripta, 2012

In this work, we report detailed investigations on the structural and magnetic properties of pure... more In this work, we report detailed investigations on the structural and magnetic properties of pure and Co-doped CeO 2 nanoparticles. All the samples, with different cobalt concentrations, were prepared by the co-precipitation method. To investigate the structural properties and phases present in the samples, systematic, x-ray diffraction measurements were performed in the θ-2θ mode. Phonon modes, from the pure and Co-doped samples, were studied by Raman scattering measurements. Surface morphology of individual nanoparticles was studied by field emission scanning electron microscopy. Interestingly, room temperature ferromagnetism is observed in, both, un-doped and Co-doped samples. The mechanisms of variation in the Raman active mode (F 2g ) and magnetization, by increasing the cobalt concentration, are briefly discussed.

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Evolution of magnetic nanophases of Ni embedded in Al_2O_3 (0 0 1) matrix by X-ray magnetic circular dichroism

We report on the element-specific magnetic characterization of Ni nanoparticles (NPs) embedded in... more We report on the element-specific magnetic characterization of Ni nanoparticles (NPs) embedded in Al 2 O 3 (0 0 1) matrix prepared by ion-implantation (Ni:5 Â 10 16 -2 Â 10 17 ions cm À2 ) technique. The X-ray diffraction studies reveal the coexistence of fcc Ni NPs of average size $8-19 nm along with the other NiO x phases. X-ray magnetic circular dichroism (XMCD) experiments demonstrate the competing nature of magnetic interactions between the Ni NPs and NiO x phases. The ferromagnetism at 10 K (for all the Ni implants) is related to the combined contribution of both phases, while the room temperature superparamagnetism at higher fluence is dominated by Ni NPs phase as confirmed by Ni L 3,2 XMCD measurements.

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Structural, electronic, and magnetic properties of Co doped SnO2 nanoparticles

Journal of Applied Physics, 2010

We present a detailed study on the structural, electronic, and magnetic properties of chemically ... more We present a detailed study on the structural, electronic, and magnetic properties of chemically synthesized Sn1-xCoxO2 (x =0.00 to 0.05) nanoparticles. X-ray diffraction and transmission electron microscope measurements were performed to analyze the crystal structure and morphology of Sn1-xCoxO2 nanoparticles. The energy dispersive x-ray analysis measurements were performed to check the possible presence of any impurity elements in the nanocrystals. The near edge x-ray absorption fine structure (NEXAFS) experiments at Sn M5,4-edge and Co L3,2-edge were performed to probe the local environment of Sn and Co ions in the SnO2 matrix. The NEXAFS at Co L3,2-edge, along with multiplet calculations, indicate that the Co is substituted at the Sn site in SnO2 matrix with +2 charge state and do not form metallic clusters and other oxide phases. The ferromagnetic nature of these materials was confirmed by x-ray magnetic circular dichroism and room temperature magnetization hysteresis loop measurements.

Effect of 100 MeV O ion beam irradiation on structural, optical and electronic properties of SnO2 thin films

Radiation Effects and Defects in Solids, 2010

In this paper, we present the impact of swift heavy ion beam irradiation on the structural, optic... more In this paper, we present the impact of swift heavy ion beam irradiation on the structural, optical and electronic properties of SnO2 thin films. Thin films were deposited using the pulsed laser deposition technique on Al2O3 substrates. Atomic force microscopy, X-ray diffraction, UV–visible absorption and temperature-dependent resistivity measurements were performed to explore the morphological, structural, optical and electronic properties of the as-deposited and irradiated samples. The peak intensity of the (200) peak was found to decrease monotonously with increasing irradiation fluence. The band gap energy of the 1×1011 ion/cm2 irradiated sample was found to increase. The electrical resistivity of the samples showed a continuous increase with the irradiation fluence.

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Evolution of magnetic nanophases of Ni embedded in Al2O3 (0 0 1) matrix by X-ray magnetic circular dichroism

Chemical Physics Letters, 2011

We report on the element-specific magnetic characterization of Ni nanoparticles (NPs) embedded in... more We report on the element-specific magnetic characterization of Ni nanoparticles (NPs) embedded in Al2O3 (0 0 1) matrix prepared by ion-implantation (Ni:5 × 1016-2 × 1017 ions cm-2) technique. The X-ray diffraction studies reveal the coexistence of fcc Ni NPs of average size ∼8-19 nm along with the other NiOx phases. X-ray magnetic circular dichroism (XMCD) experiments demonstrate the competing nature of magnetic interactions between the Ni NPs and NiOx phases. The ferromagnetism at 10 K (for all the Ni implants) is related to the combined contribution of both phases, while the room temperature superparamagnetism at higher fluence is dominated by Ni NPs phase as confirmed by Ni L3,2 XMCD measurements.

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