Magnetism and superconductivity in Sr

Anomalous magnetic properties ofSr2YRuO6

“…Since Y is a nonmagnetic ion, it is not expected to take part in the exchange interaction and hence the second interaction between the nnn is assumed to be negligible. This assumption can further be supported by the fact that the relaxation rate at the O͑3͒ site for the muons is very much smaller than the relaxation rate at the O͑1,2͒ site 8,10 since the Ru-O-Y-O-Ru pathway includes the oxygen at the O͑3͒ sites only. Whether the competition between these two interactions, however, can give rise to the observed double peak behavior needs further investigations.…”

“…In fact, the isomer-shift values from the 99 Ru Mössbauer measurements in Sr 2 YRuO 6 had confirmed the pentavalent oxidation state of Ru moments. 8,19 Even if the spin-glass state is assumed as suggested by Harshman et al, 10 the observed properties-the magnetization reversal, thermodynamic reversibility of magnetization, and two peaks in heat capacity-cannot be explained. The magnetic interactions among the ordered Ru moments can take place in two ways: ͑i͒ the -superexchange interaction between nearestneighbor ͑nn͒ Ru 5+ ions via Ru-O-O-Ru pathway and ͑ii͒ the -superexchange between the next-nearest-neighbor ͑nnn͒ Ru 5+ ions via Ru-O-Y-O-Ru pathway.…”

“…2 Even though there are no detailed experimental observations in Sr 2 YRuO 6 , many experimental results including neutron diffraction exist for Cusubstituted Sr 2 YRu 1−x Cu x O 6 compounds. [7][8][9][10] Assuming that the magnetic properties associated with the ordering of the Ru moments are not drastically altered, we can analyze the results of the SR measurements in the Cu-substituted compounds. 8,10 Both the precession frequency and relaxation rate show anomalies at ϳ30 K for muons trapped in the two possible sites: oxygen in the YRuO 4 layers ͑ O͑1,2͒ ͒ and oxygen in the SrO layers ͑ O͑3͒ ͒.…”

“…Among the Sr 2 LnRuO 6 compounds, Sr 2 YRuO 6 has captured additional interest due to the occurrence of superconductivity when Ru is partially ͑Յ15%͒ replaced by Cu. [5][6][7][8][9][10] Cu is found to get substituted at the Ru site in the YRuO 4 planes and thus the structure of the substituted compounds remains the same as that of the parent compound, without creating any additional Cu-O planes. 7 The parent compound Sr 2 YRuO 6 is known to be an antiferromagnetic insulator with the Ru moments ordering at T N =26 K. 2 The magnetic ordering temperature ͑T N ͒ was inferred as 26 K from the position of the peak in the magnetization measurements.…”

Magnetic, specific heat and 151Eu Mössbauer studies on compounds

“…The discovery of superconductivity in Cu substituted Sr 2 YRu 1Àx Cu x O 6 compounds [1] has initiated extensive studies in A 2 RRuO 6 (A ¼ alkalineÀearth metal, R ¼ rareÀearth metal) compounds. The studies are directed to understand how superconductivity can occur in these compounds which lack Cu-O planes.…”