Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 53: Superconductivity: Fe-based Superconductors - 122

TT 53.13: Vortrag

Mittwoch, 2. April 2014, 12:45–13:00, HSZ 201

Measuring detwinned EuFe₂As₂ without external pressure — •Jannis Maiwald¹, Christian Stingl¹, Sina Zapf², Shuai Jiang², Nora Bach¹, Kirk Post³, Hirale S. Jeevan¹, David Neubauer², Anja Löhle², Conrad Clauss², Dimitri Basov³, Martin Dressel², and Philipp Gegenwart¹ — ¹I.Physikalisches Institut, Georg-August-Universität Göttingen, Germany — ²1.Physikalisches Institut, Universität Stuttgart, Germany — ³Department of Physics, UC San Diego, USA

The formation of twin domains in the low temperature state of high-temperature superconductors is impeding the investigation of the in-plane anisotropy of these materials. Due to the applied pressure, mechanical clamps—commonly used to detwin crystals—induce artificial anisotropy and thus complicate the interpretation of acquired data. In case of the iron pnicides, application of typical laboratory magnetic fields did not lead to a substantial detwinning. In this talk we present a novel way to detwin EuFe₂As₂ by brief application of a small magnetic field of ∼ 1 Tesla. We will discuss magnetoresistance, magnetostriction/themal expansion and thermopower measurements, revealing that the Eu²⁺ moments support the detwinning not only below, but also above their magnetic ordering at 19K. After removing the field the system remains detwinned up to the structural and electronic phase transition at 190 K, providing a unique possibility to study the in-plane anisotropic properties of this material without the application of any external force.