The influence of pd mixing and magnetic interactions on the pre-edge peak intensity at the Co (Ni) K absorption edge in Co(Ni)_cMg_1-cO solid solutions

In this work, the variation of the pre-edge peak at the Co (Ni) K absorption edge in Me_cMg_1-cO (Me = Co, Ni) solid solutions is studied upon dilution. Its intensity is attributed to the number of |3dⁿ⁺ⁱ L + (Combining low line sign)ⁱ〉 (i > 0) ground-state configurations with oxygen 2p hole(s) denoted by L + (Combining low line sign)ⁱ. Upon dilution, the pre-edge peak intensity grows by about a factor of 1.2 in Ni_cMg_1-cO and about a factor of 2.8 in Co_cMg_1-cO. This fact is explained by an increase of the 2p(O)-3d(Me) mixing. The results obtained are in agreement with the modifications of the local atomic structure around Co²⁺ and Ni²⁺ ions, probed by extended x-ray absorption fine structure (EXAFS), and optical spectroscopies. The correlation between the concentration dependences of the pre-edge peak intensity and the Néel temperature for solid solutions is also discussed.