Electrically Controlled Intrinsic Tunneling in Dynamically Phase Separated Manganites

(La_1-yPr_y)_1-xCa_xMnO₃ (LPCMO) thin films grown on (110) NdGaO₃ (NGO) substrates show clear evidence of micrometer scale electronic phase separation. A static phase separated state is observed at low temperatures while at high temperatures (approximately above 50 K) a dynamic (fluid) phase separated state (DPS) is formed. It has been shown that in the DPS state, the ferromagnetic metallic (FMM) regions can be reorganized using a non-uniform external electric field. We used microstructured gold contact patterns on LPCMO thin films to apply a non-uniform electric field and simultaneously measure the resistance vs. temperature (R-T) behavior. The R-T graph shows a temperature independent resistance plateau at low temperatures (from about 20 K - 50 K). This behavior is a signature of tunneling. We further confirmed this tunneling behavior using current vs. voltage (I-V) measurements at low temperatures. Warming the sample up to a temperature of dynamic phase separation leads to redistribution of the FMM regions due to the non-uniform electric field between the gold electrodes. This redistribution changes the I-V characteristics from tunneling to ohmic behavior. Hence, the properties of these magnetic devices can be modified using non-uniform external electric field.