Nano-crystalline magnetic alloys of Fe-Ni and Fe-Co are fabricated by
high-energy milling. The coexistence of bcc and fcc lattice structures is
observed in some of Fe-Ni alloys, as opposed to Fe-Co ones which exhibit the
bcc phase only. The grain sizes increase linearly with the lattice strains
for Fe-Co, and exponentially so for Fe-Ni. The cut-off frequency decreases
with increasing nickel content in Fe-Ni alloys, but increases with
increasing cobalt content in Fe-Co alloys. The larger the cut-off frequency
is, the smaller the initial permeability. Resonant behaviour is observed in
the pure Fe and Fe-Ni samples, which is replaced by relaxant behaviour in
Fe-Co, implying that the Co plays an important role in hindering the
resonance. The initial permeability at 10 kHz varies inverse proportionally
with the coercivity Hc. It reaches a maximum while Hc goes to a
minimum at 7.69 at.% Ni or Co. It is interesting that average atomic
moments of nanocrystalline alloys are inconsistent with the Slater-Pauling
relation.