Mössbauer Spectra of Tetrahedral Alkali Dithioferrates (III)

Abstract

Mossbauer spectra were taken of a series of compounds with tetrahedrally coordinated (spa) iron (III) having a general formula AFeS2, where A=Na, K, Rb, Cs, over a temperature range 77°-300° K. The molar susceptibilities were also examined over the same range of temperatures. The almost temperature independence of tlEQ indicates that level separation is larger or "'kT. In contrast to the observations in the case of octahedral compounds, the increasing electronegativity of the cation increases the isomeric shift (1.S.) value. This is explained by the fact that the decreasing electronegativity of the cation increases the partial4s character at iron in the compound. Furthermore, it is pointed out that the Walker, Wertheim, and ]accarino (WW]) plot is applicable to the compounds having tetrahedrally bonded (spa) iron. The internal magnetic field in KFeS2 at -28°C is considered to result not from any magnetic transition, but from relaxation effects, whereas in the case of Na, Rb, and Cs dithioferrates it has been averaged to zero.

Spin state and exchange in the quasi-one-dimensional antiferromagnet KFeS2

“…The reports on the powder magnetic susceptibility by different investigators are conflicting, that it is temperature-independent [2,13] or that it increases with decrease in temperature below 250K [12,15] in contrast to the behaviour expected of an antiferromagnet. There are similar discrepancies in the reported values of the effective magnetic moment,/~o~, which ranges from 0-8 #B [14] to 4.6 #B [3]. A recent single crystal magnetic susceptibility report [19], however, showed a clear antiferromagnetic transition at 250 K, and a value of the magnetic moment expected for an S = 1/2 ground state for the Fe 3 + ion.…”

“…Extensive s 7Fe Mrssbauer [3][4][5][6][7][8][9][10], neutron diffraction [11][12][13], magnetic susceptibility [2,[12][13][14][15] and optical spectroscopic measurements I- [16][17][18] reported. The results and their interpretation, however, differ greatly from author to author.…”

Ionic Conducting Glasses of the Ag-Ge-Se System

“…Studies performed on Fe (III) tetrahedrally coordinated in MFeS 2 (M=Na, K, Rb and Cs) report that the quadrupolar splitting (∆) depends on the cationic radio of M [19]. 1 with those reported in the literature for the above mentioned phases, sites B 1 , B 2 and C can be associated to low spin Fe 2+ in octahedral coordination, sites D and E are attributed to high spin Fe 2+ in distorted octahedral environments while parameters corresponding to sites A can be associated to highly covalent Fe bondings.…”

Moessbauer spectrometry

“…No H (278) Alkali dithioferrate, e.g., Walker, Wertheim, Jaccarino plot (567) KFeS2 holds for these tetrahedral configurations Fe(MS04)2-6H20 AE, IS vs. T…”