Neutron and synchrotron studies of structure and magnetism of Shape Memory Alloys

Magnetic Shape Memory Alloys have attracted a large interest from the basic aspects of their structural and magnetic transitions, as well as from their possible technological applications as very rapid, contactless, high stroke actuators. The typical alloy composition for such materials is Ni-Mn-X (X= Ga, In, Sb, Sn, etc.). The electronic and magnetic structure of such alloys are on the base of the displayed properties and are object of intense study by all kind of advanced experimental and theoretical methods. Here we present a summary of recent diffraction experiments with neutron, X ray Magnetic Circular Dichroism (XMCD) and X ray Photoemission Spectroscopy (XPS) that are complementary to elucidate the electronic and magnetic character of these alloys and the changes occurring at the martensitic transformation. While rigid band models can account for most electronic features, magnetism is better described by a localized moment mainly concentrated at the Mn atoms.