Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 53: Superconductivity: Fe-based Superconductors - 122

TT 53.14: Vortrag

Mittwoch, 2. April 2014, 13:00–13:15, HSZ 201

Permanent Detwinning of EuFe₂As₂ by indirect magnetoelastic coupling — •Sina Zapf¹, Christian Stingl², Kirk Post³, Jannis Maiwald², Shuai Jiang¹, Hirale S. Jeevan², Nora Bach², David Neubauer¹, Anja Löhle¹, Conrad Clauss¹, Dimitri N. Basov³, Philipp Gegenwart², and Martin Dressel¹ — ¹1. Physikalisches Institut, Uni Stuttgart, Germany — ²I. Physikalisches Institut, Uni Göttingen, Göttingen — ³Department of Physics, UC San Diego, USA

In order to examine the in-plane anisotropy of high-temperature superconductors, sophisticated methods had to be developed for detwinning single crystals. Unfortunately, in the case of iron pnictides, typical laboratory magnetic fields do not yield an imbalance of twin domains by more than a few percent. Here we present a novel way of permanently detwinning EuFe₂As₂ single cystals in magnetic fields of less than 1 Tesla. We will discuss magneto-optical and magnetization measurements, revealing that the Eu²⁺ moments actually support the detwinning not only below, but also above their magnetic ordering at 19 K, probably by an indirect magnetoelastic coupling via the Fe²⁺ spins. Most strikingly, the detwinning remains even when the magnetic field is switched off and the resulting ratio of unbalanced twin domains of about 1:3 is robust against heating to the structural and electronic phase transition at 190 K. This provides a unique possibility to study the low temperature in-plane anisotropy of iron pnictides without the application of any external force, suitable for a wide variety of experimental techniques.