Electric-field control of ferromagnetic regions to form intrinsic tunnel junctions in dynamically phase separated manganites

Thin films of (La_1-yPr_y)_1-xCa_xMnO₃ (LPCMO) grown on (110) NdGaO₃ (NGO) substrates show micrometer scale electronic phase separation into ferromagnetic metallic (FMM) and insulating regions. Previous studies have shown that the FMM regions can be tuned in the dynamic (fluid) phase separated state using an external electric field. We have fabricated micrometer-scale gold contact patterns on LPCMO thin films to apply a non-uniform electric field and probe the magnetotransport properties of such phase separated regions, simultaneously. We have observed tunneling magnetoresistance (TMR) behavior in the magnetic easy as well as hard axis directions of LPCMO. The in-plane magnetic field sweeps near the insulator-to-metal transition temperature revealed hysteretic, resistance jumps; a clear signature of TMR. The switching field from high to low resistance reduces with the decreasing temperature. In addition, the application of high voltage along the easy axis, increases the height of the resistance peaks during field sweeps along the hard axis direction and vice versa. Hence, our data show the formation of micrometer-scale intrinsic magnetic tunnel junctions in phase separated manganites, which can be further tuned using a non-uniform electric field.