The site dependence on exchange interaction of the Fe spinel

초록

The Fe spinel FeCr2S4 and FeIn2S4 were studied on the site dependence microscopic interaction. FeCr2S4 exhibits cubic spinel structure of Fd3m, with Fe atoms occupying A site and Cr atoms occupying octahedral (B) site, whereas FeIn2S4 shows an inverse spinel, with In atoms occupying both tetrahedral (A) and octahedral (B) sites. The determined lattice constants, for FeCr2S4 and FeIn2S4, were a(0) = 9.976, 10.618 angstrom, respectively. The Neel temperatures (T-N) were found to be 175 and 15 K for the FeCr2S4 and FeIn2S4, respectively, by Mossbauer spectroscopy and magnetization measurement. It can be understood that the strength of inter-sublattice exchange interaction Fe2+ (A)-S2--Cr3+ (B) is stronger than that of the intra-sublattice exchange interaction Fe2+(B)-S2--Fe2+(B). The FeCr2S4 shows a single line resonance spectrum with an isomer shift of 0.56 mm/s at room temperature, while FeIn2S4 has an isomer shift of 0.74 mm/s and an electric quadrupole splitting (Delta E-Q) of 3.22 mm/s. The charge state of Fe ions is in ferrous (Fe2+) for the both samples. We interpret that the presence of the large Delta E-Q is attributed to the trigonal field at the octahedral site, due to Fe2+ ions occupying to octahedral B site.

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