APPLICATION OF THE GRAZING ANGLE POLARIZED NEUTRON REFLECTOMETRY TO STUDY THE MAGNETISM IN THIN-FILMS AND STRATIFIED MEDIA

From optical point of view and due to the magnetic interaction of the cold neutrons with the unpaired electron shell, magnetic materials have a neutron spin-dependent refractive index n+ [spin up] and n- [spin down]. Magnetic media such as Fe, Co and Ni react like birefringent uniaxial crystals in ordinary optics. n+ and n- are the equivalent of the ordinary and extraordinary refractive indices. The specular reflection of spin polarized neutrons which is due to the discontinuity of the magnetic induction at the surface of the ferromagnet is a sensitive probe of surface and interface magnetism. We shall first give the background of the art of polarized neutron optics. Secondly, some recent examples from surface and interface magnetism will be given to illustrate the power of this technique such as the magnetic coupling in thin films and multilayers and flux penetration in superconductors.