MOSSBAUER STUDIES OF CR-DOPED OR NI-DOPED BETA-FESI2

Iron disilicide beta-FeSi2 has two iron siites (site I and site II) wi th an equivalent number of atoms in the unit cell. We estimated the oc cupation ratio of iron between the two sites when 2 at.% Cr or Ni is d oped in beta-FeSi2. It is found that the amplitude of site I is greate r than that of site II in Ni doped beta-FeSi2 whereas the amplitude of site I is smaller than that of site II in Cr-doped beta-FeSi2. These results indicate that Ni atoms occupy site II while Cr atoms occupy si te I preferentially. The increase in the isomer shift for each sites i s observed in Ni-doped beta-FeSi2, implying that Ni doping causes enha ncement of 3d-screening of Fe-57 nuclei.