Speaker
Description
The changes in behaviour that could occur on the magnetic properties due to the structural evolution during the doping process is actually subject of our discussion. The Curie temperature (Tc) of amorphous Fe-rich alloys can be greatly enhanced by doping with light elements. In this investigation, ion implantation is used to dope Fe thin films with H, He, B, C, and N. We present a preliminary study of the structural evolution of the Fe sample during the first steps of adding impurities.
The magnetic and local structural characterization from two experimental probes, SQUID magnetometry and X-ray absorption fine structure (EXAFS), are ideal experimental techniques to perform this study. The conservation of the amorphous nature of the Fe-rich metallic glasses as-grown and implanted samples and the effect of incorporating dopant atoms in this structure is confirmed by EXAFS measurements on the Fe K-edge. EXAFS results indicate an almost negligible thermal expansion at temperatures below while normal thermal expansion takes place at higher temperatures. Such expansion seems to promote a reinforcement of the ferromagnetic interactions among Fe-Fe atoms that would account for the observed spontaneous increase in the magnetization as well as for the evolution of the coercive field. Finding the correlation between the structure and the magnetic properties could, with the use of simple sphere-stacking models allow us to create structures with desired magnetic properties. We found a shortening of the Fe-Fe bond when the dopant content was increased, which can explain the experimentally observed decrease in the magnetic moment and Curie temperature.
