  We have investigated the dc and pulsed current-induced electroresistance in
phase separated manganite Nd0.5Ca0.5Mn0.95Ni0.05O3 (NCMONi05) as a function of
temperature and magnetic field. It is shown that the negative differential
resistance which appears above a threshold current (Ic) and hysteresis in the
V-I progressively vanish with increasing period of the current pulses. However
a strong non-linearity in V-I exists even for a pulse period of 6s. The peak
voltage at Ic decreases in magnitude and shifts towards higher current values
with increasing strength of the magnetic field. The strong nonlinear behavior
and the negative differential resistance in the dc current sweep are
accompanied by a rapid increase of the sample surface temperature and therefore
primarily arise from the Joule heating in the sample. While the Joule heating
assists electroresistance in the high dc current regime, the nonlinearity in
the pulsed current sweep and the resistivity switching between a high and low
value induced by controlling the width and period of pulses can not be
explained solely on the basis of Joule heating.
