Chemical Tuning of Positive and Negative Magnetoresistances, and Superconductivity in 1222-type Ruthenocuprates

摘要

High critical-temperature superconductivity and large (colossal)magnetoresistances are two important electronic conducting phenomena found intransition metal oxides. High-Tc materials have applications such assuperconducting magnets for MRI and NMR, and magnetoresistive materials mayfind use in magnetic sensors and spintronic devices. Here we report chemicaldoping studies of RuSr2(R2-xCex)Cu2O10-d ruthenocuprates which show that asingle oxide system can be tuned between superconductivity at high hole dopingsand varied magnetoresistive properties at low doping levels. A robust variationof negative magnetoresistance with hole concentration is found in theRuSr2R1.8-xY0.2CexCu2O10-d series, while RuSr2R1.1Ce0.9Cu2O10-d materials showan unprecedented crossover from negative to positive magnetoresistance withrare earth (R) ion radius.