Temporal evolution of electrical resistance through the granular packing of Ni beads

In this paper we investigate the temporal evolution of the electrical resistance through different two-dimensional (2D) packings of Ni beads when 1 mA current is injected in them. In the first stages of measurements, resistance decreases towards a saturation value and it can be fitted with Mittag-Leffler function. Fitting parameters show that the relaxation dynamics does not depend on the type of the packing. Different packings show differences in the initial values of the resistance which is attributed to the formation of new microcontacts during the formation of the new packing. Pauses in the flow of the current cause the resistance either to decrease, increase or remain the same, depending on the packing. Longer measurements show, that after the initial drop, the resistance starts to rise which can probably be attributed to the deterioration of microcontacts between the beads. Small variations in temperature do not affect the temporal evolution of the resistance.