MAGNETIC-PROPERTIES OF 2-NM ALPHA-FE PARTICLES

Ultrafine metallic iron particles with a mean diameter of 2 nm have be en 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 al pha-Fe. The surface hyperfine field is larger than the bulk value at 5 K, but decreases rapidly with increasing temperature. The magnetic en ergy constant was found to be K approximate to (3.0 +/- 1.0) x 10(5) J m(-3).