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TT: Fachverband Tiefe Temperaturen

TT 27: Superconductivity: Fe-based Superconductors - 122

TT 27.11: Vortrag

Dienstag, 12. März 2013, 12:30–12:45, H18

Strain induced bulk superconductivity in BaFe₂As₂ thin films — •Jan Engelmann^1,2, Paul Chekhonin², Werner Skrotzki², Ruben Hühne¹, Fritz Kurth^1,2, Silvia Haindl¹, Kazumasa Iida¹, Ludwig Schultz^1,2, Holzapfel Bernhard^1,3, and Grinenko Vadim¹ — ¹IFW Dresden, P. O. Box 270116, 01171 Dresden, Germany — ²Dresden University of Technology, Department of Physics, 01062 Dresden, Germany — ³TU Bergakademie Freiberg, 09596 Freiberg, Germany

We report superconductivity in non-doped BaFe₂As₂ (Ba122) thin films grown on Fe buffered Spinel single crystalline substrates. Superconductivity was achieved in our thin films by varying the thickness of the Ba122. Increasing the thickness to a critical value of approximately 10 nm results in an increase of the superconducting critical temperature to T_c=28 K whereas films with a thickness of >100 nm do not show any superconductivity. We connect this appearance of superconductivity with the inclusion of strain in our samples. Very thin samples are fixed to the Fe buffer layer and substrate lattice constant (increased a-axis lattice constant and shortened c-axis lattice constant) whereas with increasing thickness the Ba122 layer relaxes to its bulk values. We will present via X-ray analysis the relaxation of the c-axis lattice constant coming along with structural changes showed via transmission electron microscopy (TEM) and atomic force microscopy (AFM). The bulk nature of superconductivity was determined by measurements of the critical current density and via magnetic measurements using a SQUID.