Transport properties of amorphous ferromagnets. Hall and ohmic resistivities

Simultaneous measurements are made of the ohmic resistivity (ϱ) and the Hall resistivity (ϱH) of a number of amorphous ferromagnetic Fe–Ni based alloys prepared by the rapid quenching technique. The temperature range of the experiments is 100 through 700 K and the applied magnetic fields are varied up to 2.5 T. It turns out that for all the amorphous alloys: (i) R1 ≈ 5 × 10−8 m3/As, (ii) ϱ ≈ 1.5 μΩm, (iii) ϱH has a sharp drop from which the ferromagnetic transition temperature (TC) can be determined to ≈ 5 K, (iv) the critical exponent γ ≈ 1.6 for (TC + 1) < < T < (TC + 50) K, and (v) the extraordinary Hall conductivity γHs is of the same order (≈ 5 × 104 Ω−1 m−1) as in crystalline Fe alloys. Further, in some cases (dϱ/dT) exhibits a well-defined anomaly at TC.