Magnetic properties of Fe\u3csub\u3e\u3ci\u3ex\u3c/i\u3e\u3c/sub\u3eCu\u3csub\u3e100-\u3ci\u3ex\u3c/i\u3e\u3c/sub\u3e solid solutions

In the equilibrium states, the solid solubility between Fe and Cu is negligibly small. Using vapor deposition, however, we produced FexCu100-x solid solutions over the entire composition range. All the samples were crystalline: bcc structure at the Fe-rich side and fcc structure at the Cu-rich side. The transition from bcc to fcc occurred at around x=70, where the two phases were found to coexist. The fcc alloys exhibit a magnetic dilution leading to a magnetic percolation threshold at xc≃18, rarely seen in binary Fe alloys. Below xc, only spin-glass-like ordering is observed. Across the structure transition from fcc to bcc, there is a large discontinuity in Tc, and a very slight change in the atomic volume. Surprisingly, there are no noticeable discontinuities in the magnetic moment, hyperfine field, and isomer shift. The electronic structure of these alloys is discussed based upon x-ray photoemission spectroscopy measurement

Methods of acquisition and use of firewood among hunter-gatherer groups in Patagonia (Argentina) during the Holocene

The present article examines the ways of obtaining firewood and of using it by Patagonian hunter-gatherer groups and the relationship with their high mobility. With these goals, we have selected a range of archaeological sites in varied types of vegetation: forest, forest-steppe ecotone and steppe (according to pollen reconstructions and current records) in several different latitudes of Argentinean Patagonia: Paredón Lanfré (Río Negro province); Cerro Pintado (Chubut province); Cerro Casa de Piedra 7 and Orejas de Burro 1 (Santa Cruz province). The taxa, including Nothofagus pumilio, Austrocedrus chilensis, Ribes magellanicum, Embothrium coccineum and Fabiana imbricata, found among the scattered charcoal remains in the sediments of the four Patagonian sites, show how firewood was gathered in types of vegetation similar to the ones that nowadays surround the archaeological sites. The archaeobotanical results allow us to detect differences and similarities of the supply of wood and its relationship with human mobility, site functionality and the types of occupation.Fil: Caruso, Laura Lihue. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin