Current-induced metastable resistive states with memory in low-doped manganites

The influence of dc current flow on the resistivity and phase transitions in low-doped ${\mathrm{La}}_{0.82}{\mathrm{Ca}}_{0.18}{\mathrm{MnO}}_3$ single crystals has been investigated. At low temperatures, where the resistivity strongly increases with decreasing temperature, dc current depresses resistivity in a way consistent with the domination of tunneling-conduction mechanisms. Current flow exceeding some threshold currents results in resistivity switching and metastability. Bipolar current sweep exceeding threshold currents in both positive and negative direction creates low-resistivity states in the sample. The low-resistivity state converts into a very-low- and stable-resistivity state under a stronger bipolar current sweep. Current-induced low-resistivity states are characterized by long-term memory persisting even after storing the sample for a few days at room temperature. The memory can be erased by ac current flow at high temperatures. The results are interpreted in terms of a spin-polarized tunnel conduction mechanism, which modifies phase-separation conditions along the percolation path.