The Fe1− xCoxS system ( x < 0.25); transition and the high temperature phase

The α-transition in Fe 1− x Co x S materials is examined based on electrical, magnetic and structural properties. A decrease of the transition temperature is observed with increasing alloying rate up to x co = 0.24, where the transition is completely cancelled. Beyond this critical concentration the...

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Veröffentlicht in:The Journal of physics and chemistry of solids 1987, Vol.48 (9), p.791-802
Hauptverfasser: Collin, G., Gardette, M.F., Comes, R.
Format: Artikel
Sprache:eng
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Zusammenfassung:The α-transition in Fe 1− x Co x S materials is examined based on electrical, magnetic and structural properties. A decrease of the transition temperature is observed with increasing alloying rate up to x co = 0.24, where the transition is completely cancelled. Beyond this critical concentration the materials exhibit a high-temperature FeS type behavior. The existence of hk0 reflections, with h and/or k = 2 n + 1 in the cobalt-stabilized superstructure, the high-temperature phase of FeS, establishes that the structure is hexagonal, space group P6 3 mc, with two independent metal positions, in contrast to the previously proposed tri-twinned MnP type model. The physical and structural results are discussed within the framework of conductivity by polarons. The α-transition occurs when the polaron concentration, thermally created or introduced by impurities, reaches the critical value x p ≅ 0.08. The driving mechanism for the α-transition is a reduction of the polaron dissociation energy by a temperature increase or by cobalt alloying.
ISSN:0022-3697
1879-2553
DOI:10.1016/0022-3697(87)90029-1