Showing papers by "Maheshwar Sharon published in 1996"

Pulsed laser ablation: A new route to synthesize novel superconducting compounds as oriented films

Abstract: We report here the significance of the pulsed laser ablation technique in stabilizing strained lattices that do not form by the conventional ceramic method and show that the technique offers unique possibilities to probe the structure property relationship in complicated systems. One of such systems is LuBa2Cu3O7−δ; a systematic investigation of structural (in)stability of its superconducting phase is presented here. Our analysis suggests that the system suffers from internal strain due to lower ionic radius of Lu3+; however, the structure can be stabilized only as oriented films on 〈100〉 LaAlO3, 〈100〉 SrTiO3, and 〈100〉 MgO, with excellent superconducting properties (Jc≊5.0×106 A cm−2 at 77 K). We have also investigated similar compounds having their stability close to their crystallographic limit. The important feature of these metastable phases is that they grow only as oriented films. Free energy of epitaxial growth of strained films are investigated and a simple growth model is proposed based on our observation. Importance of this growth model in explaining the superconductor–normal‐metal–superconductor type of junctions, observed in high‐Tc superconductors is highlighted.

Superconductivity and transport behavior of laser ablated Au‐added YBa2Cu3O7−δ thin films

Abstract: We report here a systematic investigation of superconducting properties of Au‐added YBa2Cu3O7−δ (YBCO) thin films in situ grown by pulsed laser ablation method. Films are highly c‐axis oriented while the corresponding bulk samples contain multiphases. The superconducting transition temperature Tc of films remains close to 90 K even for large concentration of Au (up to 10% by weight) and the critical current denisty Jc is about 5×106 A cm−2 at 77 K (in self‐field) with higher reproducibility when compared with that of undoped films of YBCO on 〈100〉 LaAlO3. Preliminary investigations indicate that Au gets rejected by the grains and dopes the grain boundaries thus improving the stability of the boundaries and hence of the films. Our result also demonstrates that pulsed laser deposition can be used to grow films of compounds that generally do not form as a single phase in bulk by the conventional solid state methods and hence offers unique possibilities in terms of exploring structure‐property relationships i...