Partial Reduction of MgFe_2O_4 with Al and Mg via Ball Milling

摘要

Nanocomposites consisting of metallic Fe particles and a nonmagnetic oxide were prepared by reducing MgFe_2O_4 with Al or Mg in a ball mill. The reaction takes place as a fast self-propagating process sometime between 0.5 and 1 h of milling. Combining XRD and Moessbauer spectroscopy reveals that the bcc Fe phase contains a few percents of dissolved Al, it has a high defect concentration, and the surface tension of the ultrafine (about 15 nm) grains results in local compressive strains. The magnetization is 25% less than expected for pure ferromagnetic Fe.