INFLUENCE OF THE SHORT-RANGE ORDER ON THE MAGNETIC-PROPERTIES OF (FECO)(75)SI15B10 METALLIC GLASSES

The short-range order of (FeyCo1-y)(75)Si15B10 metallic glasses has be en investigated by x-ray absorption spectroscopy in order to explore t he relation between the local structure and the magnetic properties. T he structural information has been further contrasted with the results obtained from the use of other local probes such as Mossbauer spectro scopy. The existence of chemical preferences leading the metalloids, B and Si, to locate near one particular metallic species, Fe and Co res pectively, is in the origin of the strong increase of the short-range order in the Co rich side, characterized by the appearance of a BCC-li ke structure around Fe for y less than or equal to 0.2. Such an effect causes a decrease of the root mean square deviation of distance betwe en Fe and its near-neighbour metallic atoms in the Co rich side (y les s than or equal to 0.5), which is strongly correlated with the decreas e of standard deviation of the distribution of hyperfine fields. The n earest-neighbour distances Fe-M and Co-M (M = Fe, Co) decrease for y l ess than or equal to 0.5, and the Co-M one shows a minimum at y = 0.06 . This behaviour has been used to explain some features of the depende nce on the composition of the Curie temperature and the spin wave stif fness constant as well as the isomer shift of the alloys.