Resistivity variation near the critical temperature in some Ni-Fe base amorphous alloys

Accurate measurements of the electrical resistivity of three Ni_80?xFe_xP₁₄B₆ alloys (with x=10, 20 and 30) were performed in the temperature interval 1.5–500 K. Resistivity (ρ) and dρ/dT behaviours near T_c for the alloys with different x values are mutually very different. In particular $\text{dρ}\text{dT}$ variation near T_c for the alloys with x=10 and 20 is Ornstein-Zernicke like while for the alloy with x=30 is of more usual energy like type. A tentative explanation of this behaviour in terms of the influence of the percolation limit on the nature of the magnetic transition is offered.