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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Ferropnictides 1

TT 40.17: Vortrag

Donnerstag, 26. März 2009, 18:30–18:45, HSZ 03

Investigation of superconductivity and magnetism in EuFe₂As₂ — •Hirale S. Jeevan and Philipp Gegenwart — I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

We present an investigation of superconductivity and magnetism in EuFe₂As₂ by doping of K, Ni,Co and P. The recent discovery of superconductivity in FeAs and related systems has a great impact in the field of superconductivity research. Superconductivity is found close to a magnetic and non-magnetic phase transition suggesting an unconventional pairing mechanism. We have synthesized single crystals and powder samples of both doped and undoped samples of EuFe₂As₂ and investigated their physical properties. We found rather unique behavior due to the additional ordering of Eu²⁺, which is absent in other systems like BaFe₂As₂,SrFe₂As₂ etc. The heat capacity, resistivity and magnetization measurements carried out at ambient pressure on the parent compound show an antiferromagnetic spin-density-wave (T_SDW) at ≈190K related to the Fe₂As₂ layers and magnetic ordering of Eu²⁺ (T_N) moments at ≈20K. Upon doping Eu with K >30%, T_SDW gets suppressed and superconductivity appears at ≈32K and also Eu²⁺ ordering suppressed to the low temperature. On the other hand,doping of Co and Ni to the Fe site suppresses the SDW transition but no SC is found, possibly due to Eu ordering which appears unchanged at ≈19K.We will also discuss the effect of P doping to the As site.

Collaboration with: C.Geibel, Z.Hossain, Deepa Kasinathan, C. F. Miclea, M. Nicklas and H. Rosner