Abstract
The magnetic properties of the unconventional mixed-valence compound Sm3 Te4have been studied by inelastic neutron scattering. Time-of-flight experiments with different incident energies (Ei = 300 meV, 67 meV and 3.2 meV) and energy resolutions have been performed on isotopic (low-absorption) 154 Sm3 Te4and on the reference compound La3 Te4 . Spectral contributions from two coexisting valence states Sm2+and Sm3+were clearly identified. In contrast to previous results for SmB6 , the spectra can be analysed in terms of well defined 4f 5and 4f 6local moments subjected to the crystal field. However, the data reveal that di- and trivalent ions, which occupy identical crystallographic sites, feel quite different crystal-field potentials. Quasielastic scattering was found to exist down to the minimum temperature (1.5 K) of the measurements, with a half-width of about 0.45 meV. This implies that spin fluctuations, with a much higher fluctuation rate than the valence fluctuations reported in a recent NMR study, exist just above the spin-glass transition.
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