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Superferromagnetism in Mechanically Alloyed fcc Fe23Cu77 with bimodal cluster size distribution
Authors: N. J. O. Silva, J. S. Amaral, V. S. Amaral , B. F.O. Costa, G. Le Caër
Ref.: J. Phys. Condens 21, 046003 (2009)
Abstract: Magnetic measurements, x-ray diffraction and Mössbauer spectroscopy were used to characterize a nanostructured fcc Fe23Cu77 at.% alloy prepared by high-energy ball-milling, addressing in particular the effect of clustering on the nature of the interacting magnetic entities. The interpretation of magnetization measurements leads to the conclusion that grains, whose mean size is ∼16 nm, contain two populations of magnetic Fe-rich nanoclusters with a bimodal size distribution. These two sets of clusters contain about 14 and 400 Fe atoms and have magnetic moments of 30 µB and 860 µB, respectively. The inter-cluster ferromagnetic interactions that lead to superferromagnetism with a Curie temperature TC∼220 K can be described by a mean field determined by the smaller clusters only, which account for 90% of the magnetization.
