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X-ray absorption spectroscopy studies of the off-center Ni 2+ ions in Ni c Mg 1-c O solid solutions

1996; SPIE; Volume: 2706; Linguagem: Inglês

10.1117/12.229142

1996-756X

Н. Миронова-Улмане, Alexei Kuzmin, J. Purāns, А. N. Rodionov,

Thermodynamic and Structural Properties of Metals and Alloys

In this work we present the x-ray absorption spectroscopy study of Ni c Mg 1-c O (0.01 <EQ c <EQ 1) solid solutions. The extended x-ray absorption fine structure (EXAFS) above the Ni K-edge was analyzed using the multi-shell fitting procedure. It was found that nickel ions are located in a distorted environment and shift upon dilution to the off- center positions. This fact follows from two main results: (1) in the first shell, the average Ni- O distance increases linearly upon dilution; (2) in the second shell, the average Ni-Ni distance remains unchanged and decreases slightly at low nickel concentration while the dependence of the Ni-Mg distance has a break at c approximately equals 0.6 and is nearly constant below and above this concentration. The obtained results are discussed in comparison with the ones from x-ray diffraction, optical spectroscopies and magnetic measurements.