Concentration dependence of the magnetic properties in amorphous Fe-P-B alloys

The concentration dependence of the magnetic properties of amorphous Fe-P-B alloys obtained by splat-cooling is discussed. For a given Fe concentration, the magnetic moment
\bar{\mu}
averaged over all atoms of material and the Curie temperature T
c
both increase with the substitution of B for P. We observed for the variation of
\bar{\mu}
and T
c
as a function of the B content the same discontinuity as that occurring between the two phases
\varepsilon
and
\varepsilon_{1}
of the crystalline Fe
3
P
1-x
B
x
compounds. We studied also the variation of
\bar{\mu}
and T
c
when one metalloid (P or B) substitutes for Fe, the other metalloid remaining constant.
\bar{\mu}
was found to decrease when the P (or B) content is increased, as expected from a rigid band model. For the same concentrations, T
c
increases. The different behaviours of
\bar{\mu}
and T
c
are tentatively explained by assuming that the amorphous Fe has two magnetic states (ferro and antiferromagnetic) as already suggested for crystalline Fe in a fcc environment.