A NEW MAGNETIC PHASE IN NANOCRYSTALLINE Fe

A. Hernando, L. Del Bianco, J.M. Rojo and C. Ballesteros

IMA-UCM-RENFE-CSIC, P.O. Box 155, Las Rozas, 28230 Madrid, Spain

Pure Fe powders, milled down to 10 nm crystallite size, have been analyzed by a combination of Moessbauer spectroscopy, high resolution transmission electron microscopy and magnetization measurements. After annealing the as- milled powders at 570 K for 1 hour, a new phase is identified with a hyperfine field of 21 T, a lower magnetic moment than bulk Fe, a magnetic order-disorder transition temperature of about 500 K and fcc crystal structure. It is tentatively interpreted as a new magnetically-ordered phase of Fe.