Magnetically induced anisotropy in amorphous alloys of Fe-Ni-P-B

The uniaxial magnetic anisotropy K
u
induced during magnetic annealing has been determined for a series of amorphous alloys of the formula (Fe
y
Ni
1-y
)
80
P
14
B
6
. In contrast to the (Fe, Ni)
80
B
20
amorphous alloys previously reported, K
u
in the present alloys has neither the composition dependence nor the temperature dependence predicted from simple pair order theory. The results strongly suggest the presence of a large contribution to the directional order anisotropy from the metalloids in the iron-rich amorphous alloys. The dependence of the uniaxial induced anisotropy on decreasing iron concentration can be accounted for by a decreasing contribution from the metalloids. A discrepancy in the temperature dependence of K
u
at high anneal temperatures is attributed to the experimental problem of too slow a quench from the anneal temperature, compared to the rather fast kinetics of equilibration at temperatures below the anneal temperature.