MAGNETIC-PROPERTIES OF 2-NM ALPHA-FE PARTICLES

Ultrafine metallic iron particles with a mean diameter of 2 nm have been prepared on a carbon support and were studied by in situ Mossbauer spectroscopy. It is found that even in these extremely small particles, containing on the average about 350 atoms, most of the atoms are in environments which are quite similar to those of iron atoms in bulk alpha-Fe. The surface hyperfine field is larger than the bulk value at 5 K, but decreases rapidly with increasing temperature. The magnetic energy constant was found to be K approximate to (3.0 +/- 1.0) x 10(5) J m(-3).