A search for magnetic resonance of ruthenium in octahedral coordination with oxygen

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• 作者：H.A. Blackstead ; W.B. Yelon ; M. Kornecki ; M.P. Smylie ; P.J. McGinn ; Q. Cai ; B.W. Benapfl ; S.D. Knust
• 关键词：Antiferromagnetic ; ESR ; Rutheno-Cuprate
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2009
• 出版时间：October 2009
• 年：2009
• 卷：321
• 期：19
• 页码：3207-3216
• 全文大小：984 K

文摘

We have searched, without success, for microwave-frequency magnetic resonance of Ru⁴⁺ and Ru⁵⁺ ions in a number of materials for which the Ru are in octahedral coordination with six oxygen. A number of ruthenates including RuO₂, SrRuO₃, Sr₃Ru₂O₇, Ba₃Ru₂NiO₉, Ba₂GdRuO₆, Sr₂YRuO₆, and Ba₂YRuO₆, which include paramagnetic, antiferromagnetic, and ferromagnetic spin configurations, have been examined. We present analysis which shows that the last material provides an optimized opportunity to detect antiferromagnetic Ru resonance for temperatures less than T_N=39 K; none is detected for frequencies as high as 35 GHz in magnetic fields up to μ_oH=2 T. This result indicates that the antiferromagnetic magnon energy gap exceeds the energy associated with the signal frequency. SrRuO₃ is a known ferromagnetic contaminant phase in the rutheno-cuprates. We report neutron diffraction measurements on SrRuO₃, finding it to have an appreciable local moment at low temperatures, 1.25(0.1)μ_B; this moment vanishes near 165 K. We show that it also fails to exhibit ferromagnetic resonance, at least in the range 10–35 GHz. As a result of the diffraction and resonance studies, it is concluded that the reports of ferromagnetic resonance in superconducting rutheno-cuprates are actually due to antiferromagnetically ordered Cu in these materials, and the presence of even a few percent of SrRuO₃ as a potential contaminant is of little importance.