Metal-to-insulator transition and magnetic ordering in CaRu1-xCuxO3
CaRuO3 is a perovskite with an orthorhombic distortion, and is believed to be close to magnetic ordering. Magnetic studies of single-crystal and polycrystalline CaRu1-xCuxO3 (0less than or equal toxless than or equal to15 at. %Cu) reveal that a spin-glass-like transition develops for xless than or equal to7 at. % Cu. The obtained value for the effective magnetic moment p(eff) =3.55 mu(B) for an x=5 at. % Cu single crystal, indicates the presence of Ru5+. 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 Cu2+/3+ substitution, induces the appearance of Ru5+ 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.