High Temperature Ferromagnetism in a GdAg2 Monolayer

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• 作者：M. Ormaza ; L. Fernández ; M. Ilyn ; A. Magaña ; B. Xu ; M. J. Verstraete ; M. Gastaldo ; M. A. Valbuena ; P. Gargiani ; A. Mugarza ; A. Ayuela ; L. Vitali ; M. Blanco-Rey ; F. Schiller ; J. E. Ortega
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：July 13, 2016
• 年：2016
• 卷：16
• 期：7
• 页码：4230-4235
• 全文大小：435K
• 年卷期：0
• ISSN：1530-6992

文摘

Materials that exhibit ferromagnetism, interfacial stability, and tunability are highly desired for the realization of emerging magnetoelectronic phenomena in heterostructures. Here we present the GdAg₂ monolayer alloy, which possesses all such qualities. By combining X-ray absorption, Kerr effect, and angle-resolved photoemission with ab initio calculations, we have investigated the ferromagnetic nature of this class of Gd-based alloys. The Curie temperature can increase from 19 K in GdAu₂ to a remarkably high 85 K in GdAg₂. We find that the exchange coupling between Gd atoms is barely affected by their full coordination with noble metal atoms, and instead, magnetic coupling is effectively mediated by noble metal–Gd hybrid s,p–d bands. The direct comparison between isostructural GdAu₂ and GdAg₂ monolayers explains how the higher degree of surface confinement and electron occupation of such hybrid s,p–d bands promote the high Curie temperature in the latter. Finally, the chemical composition and structural robustness of the GdAg₂ alloy has been demonstrated by interfacing them with organic semiconductors or magnetic nanodots. These results encourage systematic investigations of rare-earth/noble metal surface alloys and interfaces, in order to exploit them in magnetoelectronic applications.