VERNANOMAG involved four research groups: the project manager Olivier Fruchart (NANO department of the Néel Institute, Grenoble), Bruno Gilles (SIMAP, Science and Engineering of Materials and Procedures Laboratory, Grenoble), Fabrice Scheurer (IPCMS, Physics and Chemistry of Materials Institute, Strasbourg) and the DEIMOS beamline at SOLEIL, directed by Philippe Ohresser. The samples preparations have been done in Grenoble and in Strasbourg; IPCMS is also responsible for theoretical growth studies.
The Grenoble group has prepared samples of variable lattice parameters. This was a two-stage manufacturing process: first, deposition of an alloy with variable lattice parameters, then a magnetic element (iron) was deposited on this first layer, the growth of which was pseudomorphic, i.e. adopting the crystallographic structure of the substrate, in this case the variable lattice parameters. The influence of the lattice parameter on the magnetic properties of the element was then studied. Alloy nanostructures have also been created by the group of Strasbourg. The co-deposition of cobalt and palladium on a nanostructured substrate (here, Au(111)) is done by the self-organization of alloy dots. An alloy whose structure is controlled by the growth conditions: disorganized or in a core-shell structure, the palladium coating the cobalt. Mastering the manufacture of such nano-objects is the first challenge, prior to their characterization.
For this characterization, the dichroism measurements using synchrotron radiation, initially planned on the DEIMOS beamline, have been carried out in Switzerland, on the SLS SIM beamline. The measurements on DEIMOS, planned at the end of 2010, will use the preparation chambers financed by VERNANOMAG (Figure 1). These UHV chambers are associate to the cryo-magnet device, which is a superconducting magnet (coils cooled in liquid helium) where the sample can also reach low temperatures (1.5 K). Such low temperatures are mandatory to study the magnetic properties of nanostructures. These dichroism measurements are carried out under ultrahigh vacuum (10-11 mbar), because the detection is done using total electron yield which gives to the XMCD (at low energy) its surface sensitivity.
A new series of XMCD measurements are planned on the SLS SIM beamline in April 2010. The collaboration between the 4 partners is therefore continuing, as nano-objects with magnetic properties are still playing an important technological role.
