Translating reproducible phase-separated texture in manganites into reproducible two-state low-field magnetoresistance: An imaging and transport study

Abstract

In thin-film ${\text{La}}_{0.6}{\text{Ca}}_{0.4}{\text{MnO}}_{3}$, conducting-tip and magnetic force microscopy reveal a pattern of nanoscale phase separation that is reproducible across cooling runs. This pattern represents the intersection of buried three-dimensional filamentary ferromagnetic metallic pathways with the sample surface. As an interlayer in current-perpendicular-to-the-plane trilayer devices, this phase-separated material magnetically decouples ferromagnetic metallic ${\text{La}}_{0.7}{\text{Ca}}_{0.3}{\text{MnO}}_{3}$ electrodes which switch sharply. This yields sharp two-state low-field magnetoresistance that is also reproducible across cooling runs. The reproducibility and the magnitude of the resistance jump are linked to highly resistive $(\ensuremath{\sim}{10}^{\ensuremath{-}12}\text{ }\ensuremath{\Omega}\text{ }{\text{m}}^{2})$ constrained domain walls in the pathways of the phase-separated interlayer. Phase separation is normally associated with high-field colossal magnetoresistance and, therefore, its exploitation here to produce low-field effects is unusual.