K. K. Sharma

National Institute of Technology, Hamirpur, Hamīrpur, Uttar Pradesh, India

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Publications (16)18.18 Total impact

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    Dataset: jap....
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    ABSTRACT: Epitaxial thin films of SrRuO3 having thicknesses 100, 50, 25, and 12 nm have been grown on SrTiO3 (001) substrate by pulsed laser deposition technique. The thickness dependent resistivity analysis reveals the non-Fermi-liquid type behavior by obeying T1.5 temperature dependence below the transition temperature. Increase in disorder and correlation with decrease in the film thickness lead to the transition from metallic to insulating phase for 12 nm film. Magnetic studies suggest the destruction of ferromagnetism for this film. Magnetization obeys 3D mean field model for 100 nm film and 2D Ising model for 50 and 25 nm films.
    Applied Physics Letters 01/2014; 104(8):081608-081608-4. · 3.79 Impact Factor
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    ABSTRACT: We present the structural, cation distribution, electrical and magnetic studies of CoAlxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8) ferrites. The Rietveld-fitted X-ray diffraction (XRD) patterns confirm the formation of single-phase cubic spinel structures with Fd3¯m space group for all the samples. A comprehensive analysis of XRD-based cation distribution has been performed to see the effect of Al3+ ions substitution on various structural parameters such as site ionic radii, edge length, bond length and interionic distances. The dielectric constant and direct current (DC) conductivity decreases with increasing Al3+ substitution up to x = 0.4. However, with further increase in Al3+ substitution, both the dielectric constant and the DC conductivity increase. The presentation of dielectric data in the complex electric modulus form reveals the presence of a non-Debye-type relaxation behaviour in the considered ferrites. The power law behaviour of alternating current (AC) conductivity indicates a strong correlation among electrons in these systems. The isothermal magnetisation versus applied field curves with high-field slope and significant coercivity suggest that the studied materials are highly anisotropic with canted spin structures. The samples exhibit ferrimagnetic behaviour at 300 K and the magnetisation decreases with increasing Al3+ concentration. The as-prepared samples are promising candidates for various industrial applications.
    Journal of Physics and Chemistry of Solids 01/2014; 75(4):558–569. · 1.53 Impact Factor
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    Journal of Applied Physics. 01/2014; 115(1):-.
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    ABSTRACT: La0.7Sr0.3MnO3/YBa2Cu3O7/La0.7Sr0.3MnO3 (LSMO/YBCO/LSMO) heterostructures were prepared by pulsed laser deposition technique. The resistivity–temperature (ρ–T) variation and magnetoresistance effects of these heterostructures have been studied and are found to be dependent on the thickness of superconducting spacer layer. We have observed that metal–insulator (TMI) transition get suppressed with increase in thickness of the spacer layer. The maximum magnetoresistance ratio ∼70% at 266 K and ∼65% at 254 K temperature are observed for 50 nm and 100 nm spacer layers respectively. In LSMO(200 nm)/YBCO(50 nm)/LSMO(200 nm) specimen the temperature coefficient of resistance (TCR) is ∼6.63% K−1 which can be useful for bolometric performances and temperature sensors.
    Physica C Superconductivity 01/2014; 497:30–33. · 0.72 Impact Factor
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    ABSTRACT: We present the thickness dependent magneto electrical transport studies of YBCO in La0.7Sr0.3MnO3 (magnetic material)/YBa2Cu3O7 (superconductor)/La0.7Sr0.3MnO3 (magnetic material) heterostructures. The ferromagnet /superconductor /ferromagnet heterostructures were deposited on single crystal (001) SrTiO3 (STO) substrate using the pulsed laser deposition (PLD) technique. In LSMO/YBCO/LSMO films, the thickness of top and bottom La0.7Sr0.3MnO3 layers were 200nm thick, and YBa2Cu3O7 layer was 50, 100 or 200nm thick. The crystal orientations of the films were determined by X-ray diffraction (XRD) using Cu Kα radiation. The resistivity-temperature (ρ-T) variation was examined by a four probe method in the temperature range from 5K to 300K. The LSMO (200nm)/YBCO (50nm)/LSMO (200nm) film has MR ratio 69% at 4T field and 265K temperature, it increases to 76% at 250K temperature and 4T field for 100nm thickness of spacer YBCO layer. These results indicates that with the increase of spacer layer (YBCO) thickness the metal-insulator (M-I) transition temperature is decreasing.
    06/2013;
  • Rabia Pandit, K. K. Sharma, Ravi Kumar
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    ABSTRACT: We present here Structural, Cationic distribution and Dielectric study of Zn2+ substituted cobalt ferrite. A series of polycrystalline samples of Co1-xFe2ZnxO4(x = 0.2,0.4) are prepared by double sintering solid state reaction method whose phase purity and space group confirmation is done by X-Ray diffraction (XRD) and Rietveld refinement method using Fd3m space group. The cation distribution is estimated through matching of X-ray diffraction intensities of cation sensitive planes. Using cation distribution study the structural parameters like ionic radii of tetrahedral and octahedral sites, bond length and inter ionic distances are also calculated. The dielectric constant taken at room temperature from 75 kHz to 1MHz increases after Zn2+ doping.
    06/2013;
  • Pawanpreet Kaur, K. K. Sharma, Ravi Kumar
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    ABSTRACT: We present here the effects of Swift heavy ion (SHI) irradiation with 200 MeV Ag15+ ions on the structural properties of GdFeO3 epitaxial film grown on SrTiO3 (STO) substrate with (001) orientation by pulsed laser deposition (PLD). The irradiation of the film induces lattice expansion in c-axis and increases the surface roughness as compared to the pristine film, which is estimated from root mean square value of Atomic Force microscopic (AFM) images. Also an enhancement in the phase contrast for SHI irradiated film is noticed from magnetic force microscopy (MFM) images.
    06/2013;
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    ABSTRACT: We present here Structural and Magnetic study of Al3+ substituted cobalt ferrite. A series of polycrystalline samples of CoFe2-xAlxO4 (x=0.0,0.2,0.4) are prepared by double sintering solid state reaction method whose phase purity and space group confirmation is done by X-Ray diffraction (XRD) and Reitveld refinement method. The cation distribution is estimated through matching of X-ray diffraction intensities of cation sensitive planes. The amount of Fe3+ content entering at A and B site as estimated through cation distribution is further confirmed by 57Fe Mössbauer spectra taken at room temperature which indicates a decrease in hyperfine filed with Al3+ doping.
    02/2013;
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    ABSTRACT: The polycrystalline samples of GdFe1-xNixO3(x=0.0, 0.1) are prepared by solid state reaction route, their structure is analyzed by powder X-ray diffraction (XRD) and Rietveld refinement. We are also studying the behavior of dielectric constant (ɛ‧), tangent loss (tan δ) as a function of frequency from 75 kHz to 5 MHz and AC conductivity (σac) from 75 kHz to 1 MHz for both the compositions at room temperature. It is noticed that Ni3+ ion substitution results in lattice contraction and enhancement in dielectric constant, tangent loss and AC conductivity.
    International Journal of Modern Physics Conference Series. 01/2013;
  • Hardeep Thakur, Ravi Kumar, Kuldeep Kumar Sharma, Pardeep Thakur
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    ABSTRACT: Tin dioxide (SnO2) thin films were deposited on a well cleaned sapphire single crystal substrate by rf magnetron sputtering technique. After deposition, films were irradiated by swift heavy ion (SHI) irradiation at various ion fluences. We present the X-ray absorption spectra (XAS) at the oxygen K- and Sn M5,4, edge. The XAS pattern reveals the broadening of O K- and Sn M5,4, edge features with increasing ion fluence. The fraction of under-coordinated surface atoms in the SnO2 thin films increases, which is attributed to the structural distortions induced by SHI irradiations.
    AIP Conference Proceedings. 07/2011; 1349(1).
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    ABSTRACT: We report on the room temperature ferromagnetism in the swift heavy ion (SHI) irradiated TiO2 thin films by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) experiments at the O K and Ti L3,2 absorption edges. The XAS/XMCD measurements provide direct evidence of magnetic polarization of the O 2p and Ti 3d orbitals. The unquenched orbital magnetic moment within the O 2p shell is ferromagnetically coupled to the neighboring Ti moments, which illustrates the intense hybridization of the O 2p and Ti 3d orbitals induced by SHI irradiation.
    Applied Physics Letters 01/2011; 98:192512. · 3.79 Impact Factor
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    ABSTRACT: We report on the observation of a strong orbital anisotropy in the orthorhombic phase of SnO2 thin films and its modification by swift heavy ion (SHI) irradiation. Structural investigations along with the Raman spectroscopy show a significant distortion of the SnO6 octahedra after SHI irradiation. The X-ray absorption and X-ray linear dichroism (XLD) experiments provide the direct evidences of change in orbital anisotropy/electronic structure due to orbital reconstruction in the SnO2 lattice after irradiation. The XLD measurements at the O K edge confirm the deterioration in the SnO6 octahedra due to controlled structural disorder induced by SHI irradiation.
    Chemical Physics Letters 01/2011; 511:322. · 2.15 Impact Factor
  • Journal of Applied Physics 01/2011; 110:083718. · 2.21 Impact Factor
  • K Sharma, M Varshney, R Kumar
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    ABSTRACT: Following successful placement of a tracheal tube (TT), it is frequently moved from the midline to the angle of the mouth. This study investigates the tracheal tube tip position in the two fixation positions in 200 adult patients. Following tracheal intubation, a fibreoptic bronchoscope (FOB) was introduced through a swivel connector and the distances from the swivel connector to the lips, carina, tip of TT and the crico-tracheal membrane were measured with the TT in the midline and at the right angle of the mouth. The mean (SD) TT tip to carinal distance decreased from 3.60 (1.50) cm to 2.28 (1.55) cm in female patients, and 5.04 (1.43) cm to 3.69 (1.65) cm in male patients on moving the tracheal tube to the angle of the mouth. We conclude that there is a significant movement of the tracheal tube towards the carina on moving the TT from midline to angle of mouth and the depth of insertion of the tube should be adjusted accordingly.
    Anaesthesia 05/2009; 64(4):383-6. · 3.49 Impact Factor
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    ABSTRACT: The effects of 200-MeV Ag+15 ion irradiation on the optical properties of TiO2 and SnO2 thin films prepared by using the RF magnetron sputtering technique were investigated. These films were characterized by using UV-vis spectroscopy, and with increasing irradiation fluence, the transmittance for the TiO2 films was observed to increase systematically while that for SnO2 was observed to decrease. Absorption spectra of the irradiated samples showed minor changes in the indirect bandgap from 3.44 to 3.59 eV with increasing irradiation fluence for TiO2 while significant changes in the direct bandgap from 3.92 to 3.6 eV were observed for SnO2. The observed modifications in the optical properties of both the TiO2 and the SnO2 systems with irradiation can be attributed to controlled structural disorder/defects in the system.
    Journal- Korean Physical Society 61(10). · 0.51 Impact Factor