Metal-to-insulator transition and magnetic ordering in (formula presented)

(formula presented) is a perovskite with an orthorhombic distortion, and is believed to be close to magnetic ordering. Magnetic studies of single-crystal and polycrystalline (formula presented) (formula presented) reveal that a spin-glass-like transition develops for (formula presented) Cu. The obtained value for the effective magnetic moment (formula presented) for an (formula presented) Cu single crystal, indicates the presence of (formula presented) At higher Cu concentrations more complex magnetic behaviors are observed. Electrical resistivity measured on polycrystalline samples shows a metal-to-insulator transition at 51 K for only 2-at. % Cu. Charge compensation, which is assumed to be present upon (formula presented) substitution, induces the appearance of (formula presented) and/or the creation of oxygen vacancies in a crystal structure. Since the observed changes in physical properties are completely attributable to the charge compensation, they cannot be related to behaviors of a pure compound where no such mechanism is present. This study provides the criterion for “good” chemical probes for studying Ru-based perovskites.