  Kinetics of crystallization of two amorphous alloys, Fe70Cr10B20 and
Fe80Zr10B10, have been followed up by neutron thermodiffractometry experiments
performed in the two axis diffractometer D20 (ILL, Grenoble). The structural
changes are directly correlated with the temperature dependence of the
magnetization. Fe70Cr10B20 crystallizes following a two-step process: an
eutectic crystallization of alfa-Fe (bcc) and the metastable tetragonal phase
(Fe0.8Cr0.2)3B followed by another eutectic transformation to the stable phase
(Fe0.75Cr0.25)2B and more segregation of alfa-Fe. These tetragonal phases are
magnetically anisotropic, giving rise to a large increase of the coercivity.
This behaviour is similar to that of Fe80B20 alloys, with Cr atoms replacing
the Fe positions in both crystalline phases. Fe80Zr10B10 shows also a two-step
process in which two polymorphic transformations take place.
