Features of the Scaling of the Anomalous Hall Effect in (CoFeB)x(LiNbO3)100-x Nanocomposite Films Below the Percolation Threshold: Manifestation of the Cotunneling Hall Conductance?

A scaling behavior of the anomalous Hall effect resistivity rho(AHE) versus the longitudinal resistivity rho in (CoFeB)(x)(LiNbO3)(100 -) (x) nanocomposites with a low content of dispersed Co and Fe atoms (N-d similar to 4 x 10(20) cm(-3)) in an amorphous LiNbO3 matrix is studied in the range x approximate to 40-48 at % below the percolation threshold x(p) approximate to 49 at %. A logarithmic temperature dependence of the conductivity sigma similar to lnT has been observed in the range x approximate to 44-48 at %, which is transformed in the range x approximate to 40-42 at % to a square root law ln sigma proportional to -(T-0/T)(1/2), which is characteristic of cotunneling transport processes in nanocomposites. It has been found that the exponent n approximate to 0.24 in the scaling law rho(AHE)/x proportional to [rho(x)](n) coincides within an accuracy of 5% with the exponent n in a similar dependence for nanocomposites based on the (CoFeB)(x)(Al2O3)(100 -) (x) matrix with a high content N-d similar to 10(21)-10(22) cm(-3) and with the exponent n in a parametric dependence rho(AHE) proportional to [rho(T)](n) for the samples with the minimum content x approximate to 40 at %. The found features are attributed to the correlated change in the probability of cotunneling transitions in a set of more than three centers under the effect of spin-orbit coupling. The manifestation of the barrier tunneling anomalous Hall effect at granule interfaces is also possible.