Abstract

Abstract

Abstract

Abstract

The study of the co-existence of singlet superconductivity and ferromagnetism is one of the most fascinating and challenging areas of resaerch since both the phenomenon are quantum mechanically antagonistic to each other. However, the coexistence can easily be achieved in artificially fabricated superconductor–ferromagnet heterostructures and these systems offer unique opportunities to study the interplay beteween two competing order parameters and to conceive novel quantum states. Our investigations on different superconducting(S)/ferromagnetic(F) heterostructures fabricated by pulsed laser deposition reveal an intense suppression of superconductivity due to the magnetic proximity effect and the injection of spin polarised quasiparticles from the F electrode. The current dependent transport studies exhibit a significant reduction of the superconducting Tc in the S/F bilayers as compared to single S layer and strictly adhers to I2/3 de-pairing effect. Astonishingly, the superconducting Tc in YBa2Cu3O7-/ La0.5Sr0.5CoO3 bilayers is observed to be much lower as compared to YBa2Cu3O7-/La0.7Sr0.3MnO3 ones. This points to the fact that in addition to the spin polarisation of the ferromagnetic electrode, other factors such as (a) interfce transparency (b) magnetic domain state and (c) the stray field associated with the F layer might play important role in tuning the S order parameter. Magnetotransport studies reveal a remarakable reduction of activation energy (U) and a logarithmic dependence of “U” on the applied magnetic field in S/F heterostructures. This signifies the signature of the existence of decoupled 2D pancake vortices that can arise from the weakening of the S coherence length () due to the presence of F layers and the dominance of intralayer vortex-vortex interaction over the interlayer one.References:1. A.I. Buzdin, Rev. Mod. Phys. 77, 935-976 (2005).2. D. Samal, C. Shivakumara and P.S. Anil Kumar, Phys. Rev.B 77, 094510 (2008)3. D. Samal, and P.S. Anil Kumar, J. Phys.: Condens. Matter. 21, 492203 (2009) (IOP Select)4. D. Samal, Chanchal Sow and P.S. Anil Kumar, J. Phys.:Condens. Matter. 22, 295701(2010)5. D. Samal and P. S. Anil Kumar (J. Supercond. Nov. Magn. in press)Delete & Prev | Delete & NextMove to:

Abstract

Detection of flammable and toxic gases is a subject of growing importancein both domestic and industrial environments. Different deviceconfigurations based on metal oxides have been used so far. MIM is onesuch important configuration to achieve high sensitivity and fastresponse.Polycrystalline titanium dioxide was grown by thermal oxidation at 800oCon 0.25 mm thick titanium substrates with gold coating on the backsurface. Resistivity, carrier density & mobility were measured at roomtemperature. The grown oxide showed n-type conducitivity. Pd metal dots(1.5 mm dia) were deposited on the oxide surface, using e-beam evaporationtechnique, to fabricate Pd/TiOx/Ti-Au (x<2) MIM sensor structure. The I-Vstudy was carried out with 500 ppm hydrogen in the temperature range 200 -350oC and the current increased upon exposure to hydrogen. The sensitivityand the change in barrier height were calculated and were found tomaximize at 300oC beyond which the values started decreasing. The responsetime as calculated from the transient response characteristics was 16 secat 300oC.In this talk, the thin film preparation technique and associatedcharacterizations along with the sensor response will be discussed indetail.