Electronic and Magnetic Properties of Amorphous Fe-P-B Alloys

Abstract

The ternary diagram of the amorphous phase in the splatcooled Fe-P-B system was investigated by X-ray diffraction measurements. Alloys were found to be amorphous within the Fe concentration range 75 ≤ c_Fe ≤ 83 at.%. For a fixed Fe concentration, B substitutes for P over a large scale, the maximum substitution occurring for c_Fe = 80 at.%. Concentration dependence of the electronic and magnetic properties was systematically studied in alloys within the whole amorphous diagram by means of bulk magnetization $\overline \mu$ (4,2°K), Curie temperature T_c and electrical resistivity ρ measurements from 4.2°K up to the amorphous-crystalline transformation. The composition dependence of $\overline \mu$ and T_c when B substitutes for P at a constant c_Fe suggests the existence of two different short range orders in the amorphous alloys, corresponding to ɛ and ɛ₁ crystal structures in the Fe₃P_1−xB_x compounds. The concentration dependence of $\overline \mu$ and T_c when P (or B) substitutes for Fe at a constant c_B (or c_P) is explained by a comparison between the amorphous Fe and the fcc Fe. A minimum in the variation of ρ as a function of temperature T occurs at T_m. The temperature dependence of ρ is expressed by a phenomenological law:

$$ {\rm{\rho (T)}}\;{\text{ = }}\;{{\rm{\rho }}_{{\text{o}}\;}} + {\text{ A}}\;\log {\text{ T}}\;{\text{ + }}\;{\text{B }}{{\text{T}}^2}\;{\text{ + }}\;{\text{C T}}{\text{.}} $$

Work supported by the Energy Research Development Agency, Contract No. At(04–3)-822.

On leave from Laboratoire de Structure Electronique des Solides, E.R.A. 100, 4, rue Blaise Pascal, 67000 Strasbourg, France.