MOSSBAUER STUDY OF ULTRAFINE FEF2 PARTICLES

Ultrafine antiferromagnetic FeF2 particles (<10 nm) were prepared by a new technique, viz, the SF6-sensitized infrared photodecomposition of Fe(CO)5 induced by a transversely excited atmospheric (TEA) CO2 laser. The magnetic properties have been examined by57Fe Mössbauer spectroscopy. At low temperatures the magnetic hyperfine field decreases faster with increasing temperature than the hyperfine field of the bulk; this behavior appears to be consistent with collective magnetic excitations. The transition between the paramagnetic and antiferromagnetic states takes place at a higher temperature and over a broader range as compared to the bulk. FeF2 ultrafine particles are relatively sensitive to oxidation; cubic-type iron oxide is formed. © 1990 J.C. Baltzer A.G. Scientific Publishing Company.