Savidand, Grégory (2007) Interface effect on the reversal of the magnetisation of Co ultrathin films electrodeposited on Au(111). Studies by MOKE and STM in situ. PhD thesis PMC, PMC, EP/X p.129.

Alternative Locations: http://www.imprimerie.polytechnique.fr/Theses/Files/Savidand.pdf

Abstract

We developed a magneto optical device able to measure in situ the evolution of magnetization of nanostructures of Co on Au(111) electrodeposited. It contains an electrochemical cell with a continuous circulation system wich gives the possibility to change the type of solution to make multilayers deposition. The acquisition’s frequency of M/H cycle is 2 Hz. We utilized and analyzed quantitatively the results of observation’s work made by STM in situ on the morphological aspect of deposition of Co as a function of deposition potential in the range [-1.6V/MSE – 1.26 V/MSE]. Growth mode of Co is first a bilayer and then a layer by layer. During the formation of the bilayer islands density increases when the potential is more negative. Then the island size increases with the potential. The measurement of the perpendicular component of the magnetization indicates a reorientation transit!
ion from out of plane to in plane at a thickness of 1.6 monolayer. It means the coalescence of the first bilayer. When the third layer grows a maximum of magnetic susceptibility is measured at 2.8 monolayers. We deposited Cu on Co to saturate the magnetization. Thanks to that measure, we determined anisotropy constant of Co deposits upper than 2monolayers. To explain this behaviour we discussed two hypotheses. The first is that step edges atoms have stronger anisotropy energy than the atoms in the center of islands. The second is that there is a critical size for wich magnetization in the plane of the deposit.

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