Synchrotron X-ray imaging
We investigate the magnetic behavior of nanosystems, such as magnetic nanoparticles and very thin magnetic films. Many of these materials present potential interests for technological applications, for example in magnetic data storage or in the medical field. For instance, magnetic nanoparticles can be functionalized for drug delivery and cancer treatment.
One of our research thrusts has been focusing on magnetic domain memory phenomena occuring in Co based ferromagnetic films when coupled with IrMn antiferromagnetic layers. Another of our research efforts focuses on magnetic ordering and dynamics of fluctutations in assemblies of Fe based superparamagnetic nanoparticles. We are interested in characterizing the spatio-temporal behaviors of such magnetic nanostructures, as well as their response to external stresses, such as cooling/heating and magnetic field history. We use various magnetometry and imaging tools in our lab as well as synchrotron radiation to investigate these phenomena.
Magnetic force microscopy (MFM) gives the possibility to image magnetic domains, through dipolar interactions between a microscopic probe and the magnetic stray field arising from the surface of the material. We, for example, use MFM to image nanosized magnetic domains in Co based thin films and study bubble-to -stripe morphological phase transitions.
Magnetometry (MOKE, EHE, VSM) techniques allow to measure the response of a magnetic material to an external magnetic field. We have implemented an Extraordinary Hall Effect (EHE) magnetometer, a Magneto-optical Kerr effect (MOKE), as well as a Vibrating Sample Magnetometer (VSM) using a superconducting magnet giving access to magnetic field as high as 9 Tesla and low temperatures down to few Kelvins.
Synchrotron X-ray spectroscopy and scattering techniques give access to nanometric spatial scale information. By exploiting the polarization of the synchotron X-ray light and the tunability of its energy, we can probe the magnetic properties of the material. X-ray Magnetic Circular Dichroism (XMCD) allows to extract information about the spin and orbital moments in the material, while X-ray Resonant Magnetic Scatttering (XRMS) gives spatial information about magnetic ordering at the nanoscale. Furthermore, we exploit the coherence of the X-ray light and speckle correaltion techniques to unravel local magnetic disorder and magnetic memory phenomena.