Correlation between atomic ordering and magnetic properties in binary magnetic alloys

Nowadays, the development of new advanced technologies in the field of information storage and electronic devices requires a great effort in improving the performance of magnetic materials that are at the basis of the device’s functioning. Among the magnetic materials, chemically ordered binary alloys (L10, L12) are of significant interest due to the peculiar atomic arrangement within the crystallographic cell, which induces in the material, through the spin-orbit interaction, a high magnetocrystalline anisotropy. This project will aim at investigating by X-ray Absorption Spectroscopy (XAS) the degree of chemical order within different magnetic alloys and to understand the influence of specific process conditions (growth and annealing temperature, addition of a third element) on the transformation from the chemically disordered state (fcc structure) to the chemically ordered structure (fct or fcc L10, L12). Among the characterization techniques applied to investigate the structural properties at the local-scale, XAS is an effective tool to probe the chemical environment around an absorber element, and to get information on the average structural features of the materials, thus being complementary to conventional X-ray diffraction (XRD) techniques. Due to its peculiar characteristics, i.e. selectivity and high sensitivity, Extended X-ray Absorption Fine Structure (EXAFS) analysis represents the main technique to investigate the local properties in many systems whose behaviour is strongly affected by the atomic arrangement, as in the case of the L10 or L12 chemically ordered alloys, where the degree of chemical order influences significantly the magnetocrystalline anisotropy