Thermal destruction of spin-polaron bands in the narrow-gap correlated semiconductors FeGa3 and FeSb2

Abstract

We report muon spin rotation spectra in the narrow-gap semiconductors FeGa3 and FeSb2 consistent with a narrow band of small spin polarons (SPs). The characteristic sizes obtained for these SPs are RFeGa3 ≈ 0.3–0.6 nm and RFeSb 2 ≈ 0.3 nm, respectively. Such SP states are expected to originate from the exchange correlations between localized and itinerant electrons. Our data suggest that SP bands are formed at low temperature, but are destroyed by thermal fluctuations above 10 K in FeGa3 and above 7 K in FeSb2. Formation of such SP band states can explain many of the low-temperature properties of these materials.