Abstracts 2001

Abstract of Publication No. 389

Ralph Schenker, Høgni Weihe and Hans U. Güdel
Ferromagnetic Exchange in the Ground state and 4A1 Exited State of (Et4N)3Fe2F9. A Magnetic and Optical Spectroscopic Study
Inorg. Chem. 40, 4319-4326 (2001)      Full Text (PDF)      DOI-Link     

Abstract: The synthesis, crystal growth, magnetic susceptibility, and polarized optical absorption spectra in the visible and near UV of (Et4N)3Fe2F9 are reported. From singel-crystal magnetic susceptibility data and high-resolution absorption spectra in the region of the 6A1 4A1 spin-flip transition, exchange splittings in the ground and excited states are derived. Ferromagnetic ground and excited state exchange parameters JGS = -1.55cm1 and JES = -0.53cm1 are determined, respectively, and the relevant orbital contributions to the net exchange are derived from the spectra. The results are compared with those reported earlier for the structurally and electronically analogous [Mn2X9]5- pairs in CsMgX3:Mn2+ (X = Cl, Br), in which the splittings are antiferromagnetic. This major difference is found to be due to the increased metal charge of Fe3+ compared to Mn2+, leading to orbital contraction and thus to a strong decrease of the orbital overlaps and hence the antiferromagnetic interactions.

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