Mössbauer spectroscopy studies of magnetic ordering and slow paramagnetic relaxation in the helium-3 temperature range

Aspects of a carbon sorption pumped helium-3 cryostat are described with particular emphasis on applications to the study of weak exchange interactions between centers of delocalized electron spin density in a series of ionic fluorides of high spin iron (III). The novel vanishing of magnetic hyperfine splitting for T<1 K in certain charge transfer polymers based on polycyanide electron acceptors and decamethyl ferrocene is also discussed. In addition, source experiments for the ID-metamagnet Co(bipyridine) Cl₂ are presented.Supported by the U.S. National Science Foundation Division of Materials Research, Solid State Chemistry Program Grant No. DMR 8313710. The author is indebted to Drs. L. Takács, J. Takács, J.H. Zhang and M.J. Kwiecien for experimental assistance and to Dr. J.S. Miller (E.I. Dupont & Co.) for a continuing fruitful collaboration on decamethylferrocene related systems.