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CROISSANCE et MAGNÉTISME de STRUCTURES NANOMÉTRIQUES ORGANISÉES DE Co ET Rh SUR LA SURFACE DE L'Au(111)

Abstract : We have studied the magnetism and the morphology of Co, CoAu and Rh deposits on the surface of Au(111) at different temperatures, by Kerr effect, scanning tunneling microscopy, electron diffraction and Auger spectroscopy. At 300 K, by exploiting the Au(111) reconstructed surface, it is possible to form self-organized clusters, chains and films of Rh or Co from pure element deposition or from simultaneous co-evaporation of Co and Au. Contrary to films deposited at 300 K which have perpendicular anisotropy between 1.7 and 4 monolayer (ML), the ones deposited at 30 K have in-plane magnetization in the same thickness range. When these films are annealed to 300 K, a reorientation of the magnetization occurs. The evolution of the magnetism and the morphology of the film during an annealing at 450 K suggest an interdiffusion between Co and Au. This led us to study the influence of the temperature on the magnetism of CoAu alloy on Au(111). Co-evaporation of Co and Au at 30 K allows the growth of metastable alloys of non miscible elements in the bulk because of limited atoms diffusion. We have studied the evolution of Co rich alloy films between 2 and 20 ML as function of temperature. At 30 K, the films are amorphous and not magnetic. After annealing at a critical temperature, a magnetic signal of perpendicular anisotropy appears. This evolution which spreads out over several minutes or hours, depending on the thickness of the film, is due to a phase separation in the alloy film leading to a ferromagnetic percolation. Concerning the Rh, the aim was to test the existence of magnetism predicted by calculations for 1 ML deposited on a noble metal. In our experimental and growth measurement conditions, no magnetic signal has been detected. This absence of magnetic signal can be explain, at 300 K by the formation of rough films and at 30 K by the formation of a Rh-Au surface alloy in the early growth stage.
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Submitted on : Monday, November 3, 2003 - 12:29:19 PM
Last modification on : Thursday, April 23, 2020 - 2:26:22 PM
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Idrissou Chado. CROISSANCE et MAGNÉTISME de STRUCTURES NANOMÉTRIQUES ORGANISÉES DE Co ET Rh SUR LA SURFACE DE L'Au(111). Matière Condensée [cond-mat]. Université Louis Pasteur - Strasbourg I, 2002. Français. ⟨tel-00003673⟩

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