Glassy transport phenomena in a phase-separated perovskite cobaltite

Abstract

We demonstrate that single-crystal ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}$ in the semiconducting spin-glass phase $(xl0.18)$ displays a strong interplay between electronic conduction and spin-glass freezing. The resistivity exhibits a bifurcation of zero-field cooled and field-cooled temperature dependences, glassy response to application and removal of magnetic fields, and, most remarkably, a waiting time or ``aging'' effect directly in the resistivity. This behavior has its origin in the magnetoelectronic phase separation into nanoscopic ferromagnetic clusters embedded in a nonferromagnetic matrix, analogous to relaxor ferroelectrics.