Amorphous alloy Fe68.5Co5Nb3Cu1Si15.5B7 was obtained by melt spinning. Samples cut from the foil were annealed at 450, 550, 650 and 750 °C in a vacuum furnace. 57Fe Mӧssbauer spectroscopy was used to identify the crystalline phases formed and the orientation of the magnetic moments based on the refined values of the hyperfine parameters. The spectra of the samples annealed at 550, 650 and 750 °C were indicative of nanocrystallization, with the magnetic moments reoriented out-of-plane for the last sample. This behavior is in contradistinction to that of the Co-rich system, which was totally crystallized at these annealing temperatures. Our results show that small Co additions can lead to the formation of nanostructures over a whole range of annealing temperatures. A new series of Mӧssbauer spectra was obtained by recording simultaneously the intensity transmitted by a superposition of the sample with the stainless steel etalon, based on the dual absorber method previously introduced by us. The values of the recoilless fraction could be derived from the relative spectral areas. The f factor maintained values close to 0.7 for all samples measured, but dropped to 0.37 for the sample annealed at 750 °C. This behavior could be related to the presence of elastic stresses in the system, which caused the out-of-plane reorientation of the magnetic moment directions.

Equimolar mixtures of graphene and iron oxide nanoparticles were subjected to mechanochemical activation. The phase sequence was investigated using Mӧssbauer spectroscopy as function of ball milling time. For low milling times (2-4 hours) the series with hematite (Fe2O3) nanoparticles was fitted with 2 sextets, corresponding to hematite with carbon introduced in the lattice. At high milling times (8-12 hours) the same series exhibited an additional sextet with hyperfine parameters characteristic to iron carbides and a quadrupole-split doublet, which could be assigned to carbon clusters with small amounts of iron in them. The series with magnetite nanoparticles (Fe3O4) at low milling times was analyzed considering 2 sextets, corresponding to the tetrahedral and octahedral sites of magnetite. At high milling times, the magnetite series also exhibited a broad sextet representing iron carbides and the doublet associated with iron-containing carbon clusters. Supporting information was obtained by determinations of the recoilless fraction. The results were compared with those obtained by ball milling graphite with hematite and magnetite nanoparticles.