PULSED-LASER ABLATION - A NEW ROUTE TO SYNTHESIZE NOVEL SUPERCONDUCTING COMPOUNDS AS ORIENTED FILMS

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 possibilitie s to probe the structure property relationship in complicated systems. One of such systems is LuBa2Cu3O7-delta a systematic investigation of structural (in)stability of its superconducting phase is presented he re. Our analysis suggests that the system suffers from internal strain due to lower ionic radius of LU(3+); however, the structure can be st abilized only as oriented films on [100] LaAlO3, [100] SrTiO3, and [10 0] MgO, with excellent superconducting properties (J(c) approximate to 5.0x10(6) A cm(-2) at 77 K). We have also investigated similar compou nds 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 obser vation. Importance of this growth model in explaining the superconduct or-normal-metal-superconductor type of junctions, observed in high-T-c superconductors is highlighted. (C) 1996 American Institute of Physic s.