Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 1: Superconductivity - Fabrication and Characterization
TT 1.7: Talk
Monday, March 26, 2007, 11:00–11:15, H18
Evidence of superconductivity in DyRh4B4 compound — •Anke Köhler1, Günter Behr1, Günter Fuchs1, Konstantin Nenkov1, and Laxmi Chand Gupta1,2 — 1IFW Dresden, P.O.Box 270116, D-01171 Dresden, Germany — 2Guest Scientist
Several RRh4B4 (R = rare earth elements) are known to crystallize in pt (primitive tetragonal), bct (body-centered tetragonal) and the or (orthorhombic) structures. A number of them become superconducting. But so far, the Dysprosium compound is known to form only in the pt-structure and does not exhibit superconductivity. We examined the possibility of DyRh4B4 crytallizing in bct- or or-structures and exhibiting superconductivity. We synthesized polycrystalline samples containing Dy, Rh and B by arc-melting followed by an annealing process. The samples were characterized by electron EPMA and X-ray diffraction. Beside the desired DyRh4B4 composition we found a fraction of DyRh3B2 and a small amount of some other phases, which significantly got reduced by annealing. Unannealed and annealed samples contain a majority superconducting phase of the composition DyRh4B4, Tc = 4.4 K, as was shown by ac-susceptibility measurements. The as-grown samples also contain a ferromagnetic phase that is different from the superconducting one and vanishes nearly completely by annealing. In contrast, the superconducting volume fraction ( ≈ 50% ) does not noticeably change by annealing or further melting. It seems to us that the superconducting phase is orthorhombic. Further work is in progress to check this.