Structural and magnetic properties of mechanically alloyed (Fe0.5Mn0.5)xCu100−x nanocrystalline compounds

We have produced samples with nominal composition (Fe0.5Mn0.5)20Cu80 (at.%) by high-energy ball milling. A structural analysis was undertaken by means of X-ray diffraction (XRD). For milling times around 200 h, the reflections of crystalline Fe cannot be resolved and a single fcc phase is observed, having a lattice parameter larger than fcc-Cu. The grain size is 30 nm. The magnetic properties of the alloy which we observed are: (i) it has coercivities of the order of 25 mT, (ii) susceptibility in a field of 5 T shows that the alloy is polarizable, (iii) low field temperature dependence of the magnetization measured after zero field cooling (ZFC) and field cooling (FC) shows the simultaneous occurrence of two types of magnetic order with differing relaxation times. On the basis of the structural information available, we tentatively identify those types of magnetic order as corresponding to a cluster glass involving both Fe and Mn atoms and to a canonical spin glass.