On the superconducting and magnetic properties of HoNbO3-δ and EuNbO3-δ complex oxides

Complex oxide compounds of niobium and rare-earth elements, HoNbO3-delta and EuNbO3-delta, have been synthesized, and their magnetic and superconducting properties have been studied. Both these compounds are superconductors with transition temperatures T-c = 15 and 6 K, respectively. The properties of these compounds are strongly affected by the content of oxygen, in particular, T-c drops with this parameter. The compounds are paramagnetic at temperatures higher than T-c. The HoNbO6-delta magnetic susceptibility follows the Curie law, and the effective susceptibility of Ho ions mu (eff) = 9.0. The EuNbO3-delta susceptibility is described by the Curie-Weiss law with the Curie temperature Theta (c) = 4.4 K, and the effective susceptibility of Eu ions mu (eff) = 6.5. The possibility of coexistence of superconductivity and ferromagnetism in EuNbO3-delta is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.