The microstructure and electrical transport of Crx(SiO2)1−x nanogranular films with Cr volume faction x≃0.67 and 0.72 are systematically investigated. The transmission electron microscopy images and elemental mappings indicate that the films are quite inhomogeneous: some Cr granules directly connect to others while some Cr granules with size ∼1 to ∼3\,nm disperse in the SiO2 dielectric matrix. For each film, the Hall coefficient RH varies linearly with the natural logarithm of temperature, i.e., ΔRH∝lnT, above ∼60\,K, saturates at ∼60\,K, and retains the saturating value below ∼60\,K. The temperature dependence of Hall coefficient can be explained by the recent theory in granular metals and originates from \emph{virtual diffusion} of electrons through the metallic granules. For the conductivity σ, a robust Δσ∝T law is observed from ∼50 down to 2\,K. The behavior of the conductivity stems from the ``Altshuler-Aronov" correction, whose influence on the Hall coefficient is not present in the films.
@article{arxiv.1902.09264,
title = {Universal Hall coefficient correction in strongly coupled Cr-SiO$_2$ nanogranular metals},
author = {Bin Zheng and Zhi-Hao He and Zhi-Qing Li},
journal= {arXiv preprint arXiv:1902.09264},
year = {2022}
}