Abstract

We have examined the potential of Lγ4 emission spectroscopy as a new method for valence determination. Sm Lγ4 emission spectra of a mixed valence compound, SmB6, as well as Sm standard references were recorded using a multicrystal, multidetector spectrometer at 298 K. The Lγ4 spectra exhibited a large chemical shift (∼4.5 eV) and substantial profile changes depending on the Sm oxidation state. Splitting of the Sm Lγ4 band was attributed to spin-dependent atomic multiplets, and valence-dependent edge-shifts of the Sm LI XANES spectra strongly suggest that the chemical shift of the Lγ4 emission is mainly due to the screening effects of the Sm LI core. The Lγ4 spectrum of SmB6 was well reproduced by the averaged spectra of SmS and SmF3, indicating a SmB6 valence of 2.65 ± 0.03. The advantages of the Lγ4 method, including simple data treatment and no need for an excitation energy scan, will encourage its use in several areas of materials science.

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