We present results of an experimental study of structural, magnetotransport, and magnetic properties of a disordered system which consists of the strained crystalline CoFe nanogranules with the size of 2–5 nm embedded into the B-Al-O oxide matrix with a large number of dispersed Fe or Co atoms. They act in the matrix as magnetic ions and contribute essentially to the magnetization at $T$ ⩽ 25 K. The conductivity of the system follows the $\text{ln}T$ law on the metallic side of the metal-insulator transition in the wide range of metal content variation $x=49-56\mathrm{at}.\%$ that formally corresponds to the conductivity of the array of granules with strong tunnel coupling between them. We found that scaling power laws in the dependence of anomalous Hall effect (AHE) resistivity ${\rho }_{\mathrm{AHE}}$ vs longitudinal resistivity ρ strongly differ if temperature $T$ or metal content $x$ are variable parameters. The obtained results are interpreted in terms of the model of two sources of AHE emf arising from metallic nanogranules and insulating tunneling regions, respectively. We suggest that the tunneling AHE component can be caused by the recently predicted scattering assisted mechanism [A. V. Vedyayev et al., Phys. Rev. Lett. 110, 247204 (2013)] and is strongly shunted due to generation of local circular Hall current.

• Received 18 October 2016
• Revised 2 February 2017

DOI:https://doi.org/10.1103/PhysRevB.95.144202