Tuning the soft bandgap in the density of the states: The measurement of a "magnetogap" effect in carbon-black samples

We investigated the magnetic field dependence on the variable range hopping electron conduction in carbon-black samples with different volumetric densities. By applying the concepts and equations of hopping regimes when the magnetic field is applied, we were able to establish a connection between the variation of the hopping temperatures, T_ES and T_M, with the localization radius of electron conduction in carbon-black, as well as with the density of states of this material. The volumetric density dependence of all these physical quantities is also discussed. Finally, based on the magnetic field effects on the hopping parameters, we introduced the idea of a "Magnetogap" effect, indicating how the Coulomb gap changes with the magnetic field.