Magnetically ordered Cu and Ru in Ba2GdRu1-uCuuO6 and in Sr2YRu1-uCuuO6

[[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.[[incitationindex]]SCI[[booktype]]紙

Magnetic resonance and surface resistance of Ba2GdRu1-uCuuO6

[[abstract]]Using susceptibility and surface resistance measurements of Ba2GdRuO6 and of Ba2GdRu1−uCuuO6, we find that Gd, Ru, and Cu order antiferromagnetically at ∼12.5K, ∼48K, and ∼86K, respectively. The Gd electron spin resonance is exchange-narrowed by paramagnetic Ru, and is broadened to near-undetectability below TN(Ru)=48K. Ru fails lto resonate at all. Antiferromagnetic Cu exhibits a microwave frequency resonance at low fields.[[journaltype]]國外[[incitationindex]]SCI[[booktype]]紙本[[countrycodes]]NL

Magnetism and superconductivity in Sr2YRu1-uCuuO6 and Ba2GdRu1-uCuuO6

[[abstract]]We report magnetization, surface resistance (RS(T,H)), and electron spin resonance (ESR) for non-superconducting Ba2GdRu1-uCuuO6, and find that all three magnetic ions (Gd, Ru, and Cu) are ordered at low temperatures. Both ESR (Gd sublattice) and weak ferromagnetic resonance (dopant Cu) are observed while no magnetic resonance due to either paramagnetic or ordered Ru is detected. In addition, for superconducting (Tc ∼ 45 K) Sr2YRu1-uCuuO6, resistivity, muon spin rotation (μ+ SR), and 99Ru Mössbauer absorption are reported. None of the O6 materials (e.g., Sr2YRu1-uCuuO6) have cuprate planes although Cu is employed as a dopant. In Sr2YRu1-uCuuO6, the Ru moments order at a temperature (∼23 K) below that for the resistive onset of superconductivity, while the Cu orders at a higher temperature, ∼86 K. Therefore at low temperatures, this material exhibits magnetic order, coexisting with diamagnetism. The only non-magnetic layers in the superconducting O6 structure, the SrO layers, carry holes and exhibit diamagnetic screening characteristic of type-II superconductivity.[[notice]]補正完畢[[incitationindex]]SC

Location and properties of the superconducting hole-condensate in Sr2YRu1−uCuuO6

[[abstract]]The superconductivity in the compound Sr2YRu1−uCuuO6 is in the SrO layers.[[journaltype]]國外[[incitationindex]]SCI[[booktype]]紙本[[countrycodes]]NL

Magnetic susceptibility and resonance studies of ordering in Ba2GdRu1−uCuuO6

[[abstract]]Ba2GdRu1−uCuuO6 is studied by magnetic susceptibility and resonance. Gd, Ru, and Cu all order antiferromagnetically at low temperatures: Gd orders at ≈12 K, Ru at ≈48 K, and Cu at ≈86 K. A Gd antiferromagnetic resonance is observed below ≈12 K.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SC