Heterogeneous magnetism in Fe-doped bulk-amorphous and nanostructured Pd-based alloys

It has been shown in a previous work (Kapaklis et al 2005 J. Appl. Phys. 98 044319) that whereas the alloy composition Pd40Cu30Ni10P20 can be easily cast as a bulk metallic glass, a partial replacement of Pd by Fe (Pd35Cu30Ni10Fe5P20) leads to a significant crystalline fraction under the same casting conditions. In order to understand the formation and properties of these precipitates, fully amorphous ribbons of both alloy compositions were also prepared by conventional melt-spinning. Magnetic data reveal that doping with 5 at.% iron leads to the formation of nanosized crystalline inclusions in the residual bulk amorphous matrix which are completely absent in the ribbon melt-spun from the same ingot. In both types of Fe-containing alloys the amorphous matrix contains giant moments. Their size is of a few hundred (ingot) and a few tens (ribbon) of Bohr magnetons. The iron-free alloy corrected for the Langevin diamagnetism shows Pauli paramagnetism with similar susceptibility values in both the ingot and the ribbon. These values are close to the Pauli susceptibility of a control sample, a melt-spun Pd82P18 alloy which is expected to be as homogeneous as the typical binary amorphous alloys. The possible origin of different, controversial magnetic behaviors reported in the literature for Fe-doped Pd-based bulk and melt-spun alloys is discussed