Effect of Milling Time on Fe/SiO2 System Prepared by Mechanical Alloying

G. POZO LÓPEZ; S. P. SILVETTI

Buenos Aires

Congreso; At the Frontiers of Condensed Matter II: Magnetism, Magnetic Materials and their Applications; 2004

Centro Atómico Constituyentes - Comisión Nacional de Energía Atómica

A mixture of 50 % wt Fe in SiO2 was ball milled for an extended period of time in a closed vial. A planetary ball mill (Fritsch Pulverissette 5) with hardened stainless vials and balls was used. Abrasion of the mill inevitably causes contamination of the sample. Based on measurement of the Cr content in the sample we estimate a low contamination level. X-Ray diffractometry was used to obtain information about nanocrystalline structure. SEM analysis were performed to investigate the structural morphology of the samples. The ultrafine grain structures of the samples consist of magnetic nanocrystallites embedded in a residual ferromagnetic amorphous matrix. Large coercivities were found in nanostructured Fe/SiO2 granular materials prepared by mechanical milling. This behaviour was also reported in nanostructured Fe/SiO2 materials prepared by sputtering [1]. The ferromagnetic nanostructured alloys have been studied on the basis of the random anisotropy model (RAM) [2], where the effective magnetocrystalline anisotropy is deduced by considering an assembly of ferromagnetically coupled grains with magnetocrystalline anisotropies oriented at random. [1] Christodoulides, J. A. and Hadjipanayis, G. S.. Materials Science Forum 235-238 (1997). [2] Hernando A.,Vasquez M., Kulik T., Prados C.. Phys. Rev. B 51, 3581 (1995).