Interface alloying effects in the magnetic properties of Fe nanoislands capped with different materials

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We show that Fe nanoislands capped with Al, Pd, and Pt protecting layers include an alloy at the interface with the capping layer, which explains the previously known capping layer dependence on the interparticle magnetic coupling. Vibrating sample magnetometry results, for instance, are evidencing a reduction in the magnetization measured under a magnetic field of 15 mT, which is larger in the case of the Al capping and which is due to the presence of a magnetically dead interface alloy. This reduction is also observed at the atomic level using x-ray magnetic circular dichroism measurements, showing a capping layer dependence of the Fe magnetic-moment reduction that is similar for the Pd and Pt capping, and stronger for the Al capping. The trend in the magnetic properties as a function of the capping layer is explained in the light of x-ray photoemission spectroscopy results that evidence the formation of alloys at the interface between the Fe nanoislands and the capping layers. The present results highlight the strong influence of interface alloying in systems of reduced dimensionality. In particular, it is shown that the magnetic properties are strongly affected at both the atomic and macroscopic level.
©2008 The American Physical Society Support from the SRS staff during the XMCD experiments is greatly acknowledged. Financial support from the Spanish Ministerio de Ciencia y Tecnología, under Contract No. MAT2005-05524-C02 is acknowledged. Y. H. also acknowledges financial support from the “Ramón y Cajal” program, Consejo Superior de Investigaciones Científicas (CSIC) and Comunidad Autónoma de Madrid (CAM) under Project No. S-0505/MAT/0194 NANOMAGNET.