Sr2YRuO6 is an interesting compound because, upon doping with Cu, it begins to superconduct around ~49 K and becomes fully superconducting at ~23 K [25]. It also has two superconducting sister compounds that contain cuprate-planes, which superconduct slightly below about ~49 K [25]: GdSr2Cu2RuO8 and Gd2-zCezSr2Cu2RuO10 [26]. The near coincidence of the onset temperatures for superconductivity in the three ruthenate compounds, which we term the O6's (as in Cu-doped Sr2YRuO6), the O8's (as in GdSr2Cu2RuO8), and the O10's (as in Gd2-zCezSr2Cu2RuO10), makes this class of three types of compounds especially worthwhile to investigate. The simplest of these compounds is Sr2YRuO6 which is a two-layer compound with each pair of (SrO)2 layers having a YRuO4 layer in between. (See Fig. 4). Since this compound has only two kinds of layers, it is rather straightforward to select the superconducting layer: namely the SrO layer, which is the one without a strong magnetic field, and the one analogous to BaO. The YRuO4 layer is ferromagnetic in its a-b plane, with its magnetic moments stacked antiferromagnetically along the c-axis, and oriented in the ±(1,1) directions of the a-b plane. Muons in this material stop at one of two nearly identical sites: (i) the O(1,2) site which is actually two sites (due to the difference between Y and Ru) near the center of the YRuO4 layer; and (ii) the O(3) site, which is about midway between two oxygen ions on the edge of a SrO plane. Clearly the YRuO4 layer is highly magnetic (and hence rather hostile to superconductivity), while the SrO layer has an average magnetic field of zero and is the locus of superconductivity.
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