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    Title: Magnetically ordered Cu and Ru in Ba2GdRu1-uCuuO6 and in Sr2YRu1-uCuuO6
    Authors: Blackstead, Howard A.;Dow, John D.;Harshman, Dale R.;Yelon, W. B.;Chen, Ming Xing;Wu, M. K.;Chen, D. Y.;Chien, F. Z.;Pulling, D. B.
    Contributors: 淡江大學物理學系
    Date: 2001-06
    Issue Date: 2013-07-09 15:22:18 (UTC+8)
    Publisher: College Park: American Physical Society
    Abstract: Magnetic orderings of the Cu, Gd, and Ru moments in nonsuperconducting Ba2GdRu1-uCuuO6 and of the Cu and Ru moments in superconducting Sr2YRu1-uCuuO6 (whose superconducting onset temperature is ~45 K) have been studied using dc susceptibility, microwave magnetic resonance, and neutron diffraction (on Sr2YRu0.85Cu0.15O6 only). In both homologues, Cu exhibits antiferromagnetism with an ordering temperature of ~86 K (much greater than the resistive superconductivity onset transition of ~45 K), and a magnon energy gap ħωmagnon (q=0) that exceeds the microwave photon frequency of ω/2π=13 GHz. The Cu moment extracted from neutron data for Sr2YRu1-uCuuO6 is ~1.7μB at low temperature. Gd, in Ba2GdRu1-uCuuO6, is paramagnetic and displays a g=2 electron spin resonance at temperatures above ~48 K, which also persists well below ~48 K (but with a very much broadened line), and orders antiferromagnetically at ~12 K. Ru in Ba2GdRu1-uCuuO6 orders at ~48 K, but in Sr2YRu1-uCuuO6 orders at ~23 K and has a moment of ~1.6μB, extracted from neutron scattering data. In both Sr2YRu1-uCuuO6 and Ba2GdRu1-uCuuO6 the Ru orders ferromagnetically in the a-b planes with the sheet magnetization alternating in direction as one moves along the c axis, forming a net antiferromagnetic structure. We find no evidence of a Ru signature in the magnetic resonance data anywhere in the range from 3 to 300 K, a result which is consistent with the electrons being itinerant. Attempts to detect Ru magnetic resonances in various other materials have also failed. Since in Sr2YRu1-uCuuO6 the magnetic moments of the Ru and the Cu are ordered at low temperatures, its superconductivity is inconsistent with a spin-fluctuation pairing model.
    Relation: Physical Review B (Condensed Matter and Materials Physics) 63(21), 214412(11 pages)
    DOI: 10.1103/PhysRevB.63.214412
    Appears in Collections:[物理學系暨研究所] 期刊論文

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