MAGNETIC-PROPERTIES OF THE IRON-CHROMIUM FLUORIDE MIXED SERIES

The mixed fluoride series Fe1-xCrxF3 (0 less than or equal to x less t han or equal to 1), synthesized by solid state reaction, crystallizes in space group R (3) over bar c, identical to that of r-FeF3 and r-CrF 3. Mossbauer spectroscopy gives clear evidence for six-fold coordinate d trivalent high-spin iron ions and magnetic susceptibility for antife rromagnetic interactions. Both Mossbauer and susceptibility measuremen ts have clearly revealed reentrance phenomena and magnetic spin-cluste r structures; these properties which result from the presence of short -range spin correlations, are strongly dependent on the chromium conte nt and on the synthesis conditions. By accounting for magnetic studies previously discussed on the Fe1-xGaxF3 series, we can confirm the par amagnetic Curie temperature value theta(p) of r-FeF3 from the literatu re. In addition, one can conclude in favour of nonnegligible antiferro magnetic interactions between second next nearest neighbours: such a p henomenon agrees well with the presence of magnetic frustration in the se compounds, experimentally observed through the values of \theta(p)/ T-N\.