Magnetic Properties of Al-Gd-TM Glass-Forming Alloys
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day, Al-based glass-forming systems are one of hot topics in materials science. Owing to their unique physical properties in glassy state and also suitability for industrial applications, these alloys are under consideration by many research groups.[1–8] Nevertheless, some questions on mechanisms of glass formation in these materials are still unanswered. There are some
SERGEY UPOROV, Senior Researcher, and VALENTIN MITROFANOV, Chief Researcher, are with the Institute of Metallurgy, UD RAS, 101 Amundsena, 620016 Ekaterinburg, Russia. SVETLANA ESTEMIROVA and VIKTOR BYKOV, Senior Researchers, are with the Institute of Metallurgy, UD RAS, and also with the Ural Federal University, 19 Mira St., 620002 Ekaterinburg, Russia. Contact e-mail: [email protected] Manuscript submitted August 3, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
specific features that characterize these alloys. For example, the chemical composition ranges for the best glass-formers are very narrow and located at off-eutectic points, as a rule, they are noticeably shifted from eutectic concentrations to intermetallic compounds. The phase diagrams of these systems are characterized by diverse sets of compounds possessing high melting temperatures. Besides, the role of alloying elements, especially 4f-metals, in chemical bonding is still unclear for these Al-rich alloys. In numerous experimental and theoretical studies, the f-orbitals of rare earths are treated as isolated ones (the band is well localized) and so they seem not to participate in chemical bonding, see, for example.[9–15] But, the mechanism is not universal for all 4f-metals. In the case of weak localization of 4f-band, when the level is located closely to the Fermi one, 4f-electrons can be involved into chemical interaction. The case has previously been observed in Al-Ce and Al-Co-Ce alloys.[16,17] It was found that the effective magnetic moments estimated per cerium atoms were noticeably lower than that for the trivalent cerium ion because of the specific chemical bonding. The similar behavior of the rare earth magnetic moments has also been observed for other Al-based alloys and intermetallic compounds containing different 4f-metals.[18–23] It is well known that in the lanthanide series only lanthanum, cerium, gadolinium, and lutetium metals have a 5d electron in the valence band. The existence of occupied 5d orbitals for these metals suggests slight deviations in their physical and chemical properties compared with those for other rare earths. So the gadolinium metal has especial interest as a magnetic impurity in alloys because it has half-filled the 4f-level and one 5d electron in the valence band. In ternary Al-Gd-TM systems a large number of intermetallics have already been investigated, their crystal structure and magnetic properties have been revealed.[24–39] It was found that magnetism in the Al-rich compounds is determined by gadolinium atoms only, and the 3d-transition metals do not carry magnetic moments. At low temperatures these compounds demonstrate antiferromagnetic ordering, met
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