Effect of non-uniform electric field in microstructured (La_1-yPr_y)_1-xCa_xMnO₃ thin films

Thin films of the hole-doped manganite (La_1-yPr_y)_1-xCa_xMnO₃ (LPCMO) grown on NdGaO₃ (NGO) substrates show effects such as phase coexistence and colossal electroresistance (CER). Using lift-off photolithography we deposited micrometer scale gold contacts on LPCMO thin films. The geometry of these gold contacts allows us to apply non-uniform electric field across the sample. Two-probe voltage source measurements using these contacts showed overall reduction in sample resistance with increasing applied voltages between 5 V and 50 V. This electroresistance behavior is due to the realignment of the fluid-like ferromagnetic metallic (FMM) regions embedded in a charge- ordered insulating (COI) background and has been observed before with uniform electric fields. However, unlike in the case of uniform field, the non-uniform field leads to a non-monotonic change in the insulator to metal transition temperature as a function of applied voltage. This behavior is due to the dielectrophoresis of the FMM regions. We will also compare the behavior of electroresistance and the insulator to metal transition temperature under non- uniform electric field for various sizes of microstructures on LPCMO thin films.