Pressure-Induced Valence and Structural Changes in YbMn2Ge2鈥擨nelastic X-ray Spectroscopy and Theoretical Investigations

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• 作者：Ravhi S. Kumar ; A. Svane ; G. Vaitheeswaran ; Y. Zhang ; V. Kanchana ; M. Hofmann ; S. J. Campbell ; Yuming Xiao ; P. Chow ; Changfeng Chen ; Yusheng Zhao ; Andrew L. Cornelius
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：January 18, 2013
• 年：2013
• 卷：52
• 期：2
• 页码：832-839
• 全文大小：475K
• 年卷期：v.52,no.2(January 18, 2013)
• ISSN：1520-510X

文摘

The pressure-induced valence change of Yb in YbMn₂Ge₂ has been studied by high pressure inelastic X-ray emission and absorption spectroscopy in the partial fluorescence yield mode up to 30 GPa. The crystal structure of YbMn₂Ge₂ has been investigated by high pressure powder X-ray diffraction experiments up to 40 GPa. The experimental investigations have been complemented by first principles density functional theoretical calculations using the generalized gradient approximation with an evolutionary algorithm for structural determination. The Yb valence and magnetic structures have been calculated using the self-interaction corrected local spin density approximation. The X-ray emission results indicate a sharp increase of Yb valence from v = 2.42(2) to v = 2.75(3) around 1.35 GPa, and Yb reaches a near trivalent state (v = 2.95(3)) around 30 GPa. Further, a new monoclinic P1 type high pressure phase is found above 35 GPa; this structure is characterized by the Mn layer of the ambient (I4/mmm) structure transforming into a double layer. The theoretical calculations yield an effective valence of v = 2.48 at ambient pressure in agreement with experiment, although the pure trivalent state is attained theoretically at significantly higher pressures (above 40 GPa).