Valence electronic structure of Fe and Ni in FexNi1-x alloys from relative K X-ray intensity studies

K beta -to-K alpha X-ray intensity ratios of Fe and Ni in pure metals and in FexNi1-x alloys for different compositions x (x = 0.20, 0.50, 0.58) have been measured following excitation by 59.54 keV gamma -rays from a 200 mCi Am-241 point-source. For certain alloy compositions the K beta -to-K alpha intensity ratios of Fe and Ni differ considerably from those obtained for the pure metals. The 3d electron populations of Fe and Ni have been estimated by comparing the measured K beta -to-K alpha ratios with the results of multiconfiguration Dirac-Fock (MCDF) calculations. Our results for the 3d electron populations of solid iron and nickel agree reasonably well with the earlier results of band structure calculations. in the case of alloys significant changes in the 3d electron population of Fe and Ni are observed for certain alloy compositions. These changes can be explained by assuming rearrangement of electrons between 3d and (4s,4p) valence band states of the individual metal atoms. For the alloy composition x = 0.2 the change in the 3d electron population of Ni is the largest and has the opposite direction than in the case of other two alloy compositions. The totally different valence electronic structure of Fe0.2Ni0.8 alloy seems to explain the special magnetic properties of this alloy. (C) 2000 Elsevier Science Ltd. All rights reserved.