Extraordinary Hall effect in (Ni80Fe20) x(SiO2)1-x thin films

Abstract

The extraordinary Hall effect (EHE) in ferromagnetic samples is generally attributed to scatterings of iterant electrons in the presence of spin-orbit interactions. In this work, our study of the thickness dependence of the EHE in the (Ni80Fe20)x(SiO2)1-x system showed the spontaneous Hall resistivity, ρxyS to be quite independent of the film thickness while the Hall coefficient, R s (≡ρxyS/MS, where M S is the saturated magnetization), increased monotonically owing to a depression in MS. We point out that the independence of ρxyS with reducing thickness could arise if the morphological structure of the sample becomes two dimensional with decreasing film thickness, which is expected from classical percolation theory. We also find in the (Ni80Fe20)x(SiO2) 1-x system (with varying x) that ρxyS∝ρxxγ where γ=0.53, which disagrees with the value of 2 frequently attributed to the side jump effect, but which can be explained in terms of the more general form ρ xyS=ρxxΔye/ ΛSO, where Δye is the side jump displacement and ΛSO is the spin-orbit mean free path.