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 μ averaged over all atoms of material and the Curie temperature Tcboth increase with the substitution of B for P. We observed for the variation of μ and T_c as a function of the B content the same discontinuity as that occurring between the two phases\varepsilonand\varepsilon_{1}of the crystalline Fe_3P_(1-x)B_x compounds. We studied also the variation of μ and T_c when one metalloid (P or B) substitutes for Fe, the other metalloid remaining constant. μ 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 μ 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