Magnetism has recently been observed in nominally nonmagnetic iron disilicide in the form of epitaxial γ-FeSi2 nanostructures on Si(111) substrate. To explore the origin of the magnetism in γ-FeSi2/Si(111) nanostructures, we performed a systematic first-principles study based on density functional theory. Several possible factors, such as epitaxial strain, free surface, interface, and edge, were examined. The calculations show that among these factors, only the edge can lead to the magnetism in γ-FeSi2/Si(111) nanostructures. It is shown that magnetism exhibits a strong dependency on the local atomic structure of the edge. Furthermore, magnetism can be enhanced by creating multiple-step edges. In addition, the results also reveal that edge orientation can have a significant effect on magnetism. These findings, thus, provide insights into a strategy to tune the magnetic properties of γ-FeSi2/Si(111) nanostructures through controlling the structure, population, and orientation of the edges.

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Reducing fuel consumption has been a driving factor for researchers and manufacturers to continually develop improved methods for reducing the weight of automobiles or lightweighting. These vehicle lightweighting demands have directed researchers to look to using materials that are typically more difficult to manufacture in their studies. As a result, friction stir processing techniques are being looked at more closely. There are advantages to using friction stir methods. Dissimilar metals can be welded and fine-grained products can be created using friction stir methods to name a few. It can be an ideal solution for manufacturing high-conductive metals and alloys. Foamed aluminum tube similar to the one shown by Yoshiko Hangai et al [1] can be formed using the proposed process which could be used to develop lightweight automobile components. This paper provides preliminary results and insights gained when fine metal powders were used in a friction stir back extrusion (FSBE) setup. The tooling consisted of a D2 tool steel die with an H13 rotating probe mounted in a CNC mill. Within the die, commercially pure aluminum powder was topped by an aluminum cap with a milled pocket in the center. This pocket was used to locate the spin tool in the center of the cap and reduce the potential for the tool to drift and deflect. The cap was also used for compacting the powdered aluminum. X-ray diffraction indicated that Al13Fe4 was formed, indicating that the temperature within the die reached a minimum of 800°C and also indicated that the powder had the potential to partially sinter and melt.