Valence instability of europium in EuCo₂Si₂

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• 作者：Paweł ; Maś ; lankiewicz and Jacek Szade
• 关键词：EuCo₂Si₂ ; Ferromagnetism ; Surface valence transition ; Unstable valence of europium
• 刊名：Journal of Alloys and Compounds
• 出版年：2006
• 出版时间：26 October 2006
• 年：2006
• 卷：423
• 期：1-2
• 页码：69-73
• 全文大小：183 K

文摘

EuCo₂Si₂ intermetallic compound was synthesised and characterised by X-ray powder diffraction, electric resistivity, magnetic susceptibility and X-ray photoelectron spectroscopy. No sign of magnetic ordering could be depicted from the temperature dependence of electrical resistivity, whereas two ferromagnetic-like transitions were observed in the temperature dependence of the magnetic susceptibility: at 73(1) and at 21(2) K. This magnetic behaviour could be attributed to small clusters containing divalent europium ions originating from local chemical disorder embedded in a matrix containing trivalent europium ions (effective europium valence was found to be 2.94(1)). X-ray photoelectron spectroscopy study indicates a surface valence transition and a dramatic change of europium valence caused by Ar⁺ sputtering, probably due to local disorder introduced.