X-RAY-ABSORPTION EDGES IN PLATINUM-BASED ALLOYS .2. INFLUENCE OF ORDERING AND OF THE NATURE OF THE 2ND METAL

Changes in the electronic structure of platinum-3d transition single-c rystal alloys (Pt(1-x)M(x) with M = Fe, Co, and Ni) are studied as a f unction of composition, order and nature of the 3d metal. These change s are detected by using synchrotron radiation to analyze the absorptio n edges. Both the Pt L(II) and L(III) edges and the 3d metal K edge ex hibit correlated changes, which are most sensitive to the minority ele ment in the alloy. The modifications on the Pt L(II) and L(III) edges are interpreted as resulting from a variation of the number of holes i n the 5d band, corresponding to an electron transfer to platinum from the 3d metal. The corresponding changes observed on the 3d metal K edg e point to a population rearrangement between the probed levels origin ating from the atomic 3d, 4s, and 4p levels. An effect of ordering has also been observed in the Pt-Co alloys the magnitude of which is grea ter at the Co K-edge for the lowest concentration of this element. Fin ally, we compare our results to available calculations and experimenta l results obtained by other techniques.