It is shown that progressive crystallization of nonmagnetostrictive Co-base
d metallic glass (VITROVAC 6030) leads to an increase of coercivity by more
than three orders of magnitude. The mechanisms responsible for this phenom
enon are interpreted showing that the main source for the giant increase of
the coercivity is the pinning effect on the domain walls originating from
the created crystallites of the size much smaller than the domain width (co
rrelation length for ferromagnetic exchange interactions). It is also shown
that gradually devitrified non-magnetostrictive metallic glass is an excel
lent model material for verification of Neel's theory describing the Raylei
gh rule.