Growth and magnetism of self-organized CoxPt1-x nanostructures on Au(111)
Résumé
The structural and magnetic properties of self-organized CoxPt1-x nanostructures grown by codeposition at room temperature on Au(1 1 1) are reported. The samples have been imaged by scanning tunnelling microscopy and characterized by x-ray magnetic circular dichroism in the same ultra-high vacuum setup. We observe that the ordered growth is preserved for a large range of Pt concentrations. The magnetization cycles as functions of the magnetic field angle and the temperature are well reproduced by a simple model, giving a good estimation of the magnetic anisotropy distributions in these assemblies of nanostructures. The initially out-of-plane anisotropy for pure Co nanostructures strongly decreases until it lies in-plane for a 40% Pt concentration. This spin reorientation transition and the measured broadening of the switching field distribution with x are discussed using a phenomenological pair model that reproduces well the main magnetic properties of CoxPt1-x epitaxial nanostructures.