On the superconducting and magnetic properties of HoNbO sub(3- delta ) and EuNbO sub(3- delta ) complex oxides

Complex oxide compounds of niobium and rare-earth elements, HoNbO sub(3- delta ) and EuNbO sub(3- delta ), have been synthesized, and their magnetic and superconducting properties have been studied. Both these compounds are superconductors with transition temperatures T sub(c) = 15 and 6 K, respectively. The properties of these compounds are strongly affected by the content of oxygen, in particular, T sub(c) drops with this parameter. The compounds are paramagnetic at temperatures higher than T sub(c). The HoNbO sub(3- delta ) magnetic susceptibility follows the Curie law, and the effective susceptibility of Ho ions mu sub(eff) = 9.0. The EuNbO sub(3- delta ) susceptibility is described by the Curie-Weiss law with the Curie temperature theta sub(c) = 4.4 K, and the effective susceptibility of Eu ions mu sub(eff) = 6.5. The possibility of coexistence of superconductivity and ferromagnetism in EuNbO sub(3- delta ) is discussed. copyright 2001 Elsevier Science B.V.