Interdiffused layers in antiferromagnetically coupled Fe/Si multilayers studied by soft-X-ray fluorescence spectroscopy

We measured the Si L_2,3 fluorescence spectrum of an antiferromagnetically coupled Fe (3.0 nm)/Si (1.3 nm) multilayer using undulator synchrotron radiation. We estimated the chemical composition and thickness of Fe suicide layers formed by interdiffusion by curve fitting analysis using the fluorescence spectra of amorphous Fe suicides. We clarified that the amorphous Si layer of 1.3 nm thickness changed in its middle region into amorphous FeSi₂ of 0.7 nm thickness, which plays an important role in the strong antiferromagnetic exchange coupling in the Fe/Si multilayer. It was also confirmed that soft-X-ray fluorescence spectroscopy has a high potential for analyzing buried interfaces nondestructively.