Negative differential resistance and pulsed current induced multi-level resistivity switching in charge ordered and disordered manganites

We have investigated direct and pulsed current induced electroresistance in two manganites with different electronic and magnetic ground states: charge-orbital ordered 50 % Ca doped NdMnO3 and 50 % Mn doped LaNiO3. It has been shown that negative differential resistance observed at high current density in these compounds is related to Joule heating. However, bi-level and multi-level resistivity switching induced by variations in pulse width and pulse period at low current density can not be attributable to Joule heating alone. We discuss possible origins.