Giant Hall effect in nonmagneticMo/SnO2granular films

Abstract

We have measured the resistivities and Hall coefficients, ${R}_{H}$, of a series of nonmagnetic ${\text{Mo}}_{x}{({\text{SnO}}_{2})}_{1\ensuremath{-}x}$ nanogranular films with the Mo volume fraction $x$ ranging from $\ensuremath{\sim}0.29$ to 1. We found that the magnitude of ${R}_{H}(2\text{ }\text{K})$ largely increased by a factor of $\ensuremath{\sim}800$ as $x$ was reduced from $\ensuremath{\sim}0.8$ to $\ensuremath{\simeq}0.36$. Then, it slightly decreased with a further decrease in $x$ down to $\ensuremath{\simeq}0.32$, which was determined to be the classical percolation threshold, ${x}_{c}$, from the resistivity dependence on $x$. This nearly 3 orders of magnitude enhancement in ${R}_{H}$ at a metal volume fraction $x>{x}_{c}$ is explained in terms of the recent theoretical concept of the local quantum-interference effect induced giant Hall effect in granular systems.