Electric-field-induced insulator–metal transition in Pr0.5Ca0.5MnO3 thin films in ramp-type junctions

A large decrease in the electrical resistance of the junction was observed with an applied voltage of several volts in small area ramp-type junctions, ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{\text{7−δ}}/{\mathrm{Pr}}_{\text{0.5}}{\mathrm{Ca}}_{\text{0.5}}{\mathrm{MnO}}_{\text{3−z}}/{\mathrm{SrRuO}}_3.$ The lowest resistivity of the ${\mathrm{Pr}}_{\text{0.5}}{\mathrm{Ca}}_{\text{0.5}}{\mathrm{MnO}}_{\text{3−z}}$ barrier layer attained was ${\text{∼10}}^0\mathrm{\hspace{0.17em}\Omega }\mathrm{cm},$ which is much lower than the previously observed resistivities in the electric-field-induced metallic states in a single crystal of ${\mathrm{Pr}}_{\text{0.7}}{\mathrm{Ca}}_{\text{0.3}}{\mathrm{MnO}}_3$ or in stacked junctions with a ${\mathrm{Pr}}_{\text{0.5}}{\mathrm{Ca}}_{\text{0.5}}{\mathrm{MnO}}_{\text{3−z}}$ barrier. The lowest resistivity is still much larger than that of the fully ferromagnetic metallic states induced by a magnetic field. However, it was found that the lowest resistivity is not intrinsic and that it is limited by a series resistance caused by the ${\mathrm{SrRuO}}_3$ electrode, including contact resistances. The lower resistivity can be reached using an electrode with a lower resistance.