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

Abstract Complex oxide compounds of niobium and rare-earth elements, HoNbO3−δ and EuNbO3−δ, have been synthesized, and their magnetic and superconducting properties have been studied. Both these compounds are superconductors with transition temperatures Tc=15 and 6 K, respectively. The properties of these compounds are strongly affected by the content of oxygen, in particular, Tc drops with this parameter. The compounds are paramagnetic at temperatures higher than Tc. The HoNbO3−δ magnetic susceptibility follows the Curie law, and the effective susceptibility of Ho ions μeff=9.0. The EuNbO3−δ susceptibility is described by the Curie–Weiss law with the Curie temperature Θc=4.4 K, and the effective susceptibility of Eu ions μeff=6.5. The possibility of coexistence of superconductivity and ferromagnetism in EuNbO3−δ is discussed.