Strong T_c dependence for strained epitaxial Ba(Fe_(1-x)Co_x)_2As_2 thin films

摘要

Ba(Fe_(1-x)Co_x)_2As_2 superconducting thin films have been grown on SrTiO_3, (La,Sr)(Al,Ta)O_3, LaA1O_3, and YAlO_3 (YAO) single crystal substrates by pulsed laser deposition. All the films, except on YAO, have been grown epitaxially without buffer layers. The films deposited on YAO contained 45° in-plane rotated grains and showed a broad superconducting transition. The onset T_c of the films is observed to increase from 16.2 to 24.5 K with increasing c/a, mainly due to a slight distortion of the AsFe_4 tetrahedron. From this correlation, we expect that higher superconducting transition temperatures than 24.5 K in a strained epitaxial film may be possible.