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Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 100: Frustrated Magnets - Pyrochlore Oxides

TT 100.9: Vortrag

Donnerstag, 15. März 2018, 17:45–18:00, H 3005

Magnetic semimetallic state in pyrochlore ruthenate Cd2Ru2O7 — •Marian Blankenhorn1, Tomohiro Takayama2, Jürgen Nuss2, Robert Dinnebier2, Alexander Yaresko2, and Hidenori Takagi1,21University of Stuttgart, Stuttgart, Germany — 2Max Planck Institute for Solid State Research, Stuttgart, Germany

In pyrochlore oxides with the chemical composition A2B2O7 strong geometrical frustration gives rise to interesting phenomena such as spin-ice behavior. Metallic pyrochlore oxides also show a variety of electronic phases including superconductivity in Cd2Re2O7 and a metal-insulator transition (MIT) in Tl2Ru2O7. While many Ru4+ pyrochlores have been intensively studied, only three Ru5+ pyrochlores, A2Ru2O7 (A=Hg, Ca, Cd), are known so far. While Ca2Ru2O7 remains metallic at low temperatures showing spin-glass behavior, Hg2Ru2O7 undergoes a MIT at around 100 K. For Cd2Ru2O7 the formation of a SDW was proposed based on a drop of magnetic susceptibility and an anomaly in resistivity but no detailed information is available. We obtained single crystals of Cd2Ru2O7 by high pressure synthesis. Both magnetic susceptibility and resistivity exhibit a sharp drop at around 105 K. This transition accompanies a loss of carriers, indicating a low-carrier metallic state at low temperatures. The LDA + U band calculation suggests an antiferromagnetic semimetallic ground state with possibly all-in all-out magnetic order. We argue that Cd2Ru2O7 displays a unique transition where magnetic order induces a coherent semimetallic state out of an incoherent paramagnetic bad-metal.

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