[show abstract][hide abstract] 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
[show abstract][hide abstract] 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.
[show abstract][hide abstract] ABSTRACT: We present the thickness dependent magneto electrical transport studies
of YBCO in La0.7Sr0.3MnO3 (magnetic
(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.
[show abstract][hide abstract] 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.
[show abstract][hide abstract] 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.
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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