We present here the results obtained in the study of the magnetic properties of solids. The use of X-rays is today a very well established technique, which is highly complementary to those involving neutrons.

The examples described here have been obtained on 9 different beamlines and concern six different techniques (compton scattering, nuclear scattering, magnetic scattering, dichroism, emission spectroscopy, powder diffraction). Quite often the experiments are done near an absorption edge, giving direct information on the element and the electron shell.

Until recently, resonant magnetic scattering was mostly used to study elements that have a magnetic moment. The results described below on the uranium compounds show that very interesting information can be obtained at the anion K edge, specially if combined with dichroism measurements. The size of the signal observed in the dichroism experiment is astonishing: 250 times larger than the amplitude at the iron K edge in pure ferromagnetic iron! In the magnetic scattering experiment the signal is also very strong and, from polarisation analysis, seems to correspond to a dipole transition. However it is obvious that the signal does not arise from a simple magnetic dipole located at the non-magnetic element because it would have been seen easily by neutrons. The effect is more subtle ­ probably involving a hybridisation of anion p orbitals and uranium 5f magnetic states.

Since the discovery in 1988 of the giant magneto-resistance in magnetic multilayers, a lot of experiments have been performed by various techniques to study the magnetic properties of systems with reduced dimensionality (thin films, clusters, dots, etc.). This is due to the fact that the magnetic properties of a material can be modified by changing the structural parameters. This is nicely illustrated below by the study of one-dimensional nanostructures and by the use of nuclear scattering to observe, for the first time, rotation of the Fe moments in 10 successive Fe layers sandwiched between fcc-Co(100) layers.