Temperature dependence of the hall effect in amorphous Ni-Si-B alloys between 1.5 and 290 K: Evidence for magnetic ordering near a resistance minimum

Abstract

The Hall effect in the metallic glasses Ni 76Si 12B 12, Ni 78Si 8B 14 and Ni 80Si 10B 10 has been measured as a function of temperature (1.5 ≤ T ≤ 290 K) and magnetic field (B < ∼ 1.2 Tesla). At room temperature the Hall resistivity ρ H is negative and depends linearly on the magnetic field for all three compositions. With decreasing temperature Ni 80Si 10B 10 exhibits a negative spontaneous Hall coefficient and a transition to ferromagnetism at about 110 K. In case of Ni 76Si 12B 12 and Ni 78Si 8B 14 an anomalous part contributes below ∼ 40 K and ρ H changes from negative to positive sign at about 9 K. For these two alloys we find that the initial slope of the ρ H(B) curves follows a Curie-Weiss law with Tθ ≈ 0 K and the anomalous contribution of the Hall resistivity can be described by a Brillouin function for superparamagnetism.