Anomalous Hall effect in monodisperse CoO-coated Co nanocluster-assembled films

We have fabricated the uniform CoO-coated Co nanocluster-assembled films at various oxygen gas flow rates (f(o)) by using a plasma-gas-condensation method and studied their anomalous Hall effect (AHE). The longitudinal resistivity (rho(xx)) of all the films exhibits a minimum at a temperature of T-min. With the increase of f(o), T-min, shifts from 150 to 300 K and has no longer change when f(o) is up to 0.10 sccm. The saturated AHE resistivity (rho(A)(xy)) presents a near linear increase as f(o) rises. The anomalous Hall coefficient (R-s) at f(o) = 0.20 sccm is 4.9 x 10(-9) Omega cm G(-1) at 300 K, which is almost three orders of magnitude larger than bulk Co. Moreover, at f(o) = 0 and 0.05 sccm, the scaling exponents gamma = 1.2 and 1.24 in rho(A)(xy) proportional to rho(gamma)(xc) are obtained in the region of 325-375 K; At f(o) = 0.10, 0.15 and 0.20 sccm, rho(A)(xy) decreases with the increase of rho(xx) on a double-logarithmic scale, following a new scaling relation of log(rho(A)(xy)/rho(xx)) = a(0) + b(0) log rho(xx) in two temperature ranges of 5-300 K and 325-375 K. (C) 2015 Elsevier B.V. All rights reserved.