Superconductivity in quaternary niobium oxynitrides containing main group elements (M=Mg, Al, Si)

Niobium compounds continue to be an interesting family of superconductors, with the recent addition of oxynitrides to it, which can be categorized as low-Tc superconductors (LTS) because they exhibit superconductivity below Tc∼17 K. In this paper, we report the superconducting properties of three members of the family of niobium oxynitrides, viz. (Nb0.89Al0.11)(N0.84O0.16), (Nb0.95Mg0.05)(N0.92O0.08) and (Nb0.87Si0.09□0.04)(N0.87O0.13). Low temperature dc and ac magnetization measurements have been performed. In addition, heat capacity has been recorded at low temperature under applied magnetic fields. A detailed analysis of the data is presented.

The doped Si oxide accompanied with some amount of cation vacancy in cubic NbN lattice induces relatively large magnetic hysteresis on isothermal hysteresis loops at 5 K of the dc magnetization up to 5 T among the four niobium oxynitrides containing main group elements, Nb1.00(N0.98O0.02); (Nb0.95Mg0.05)(N0.92O0.08); (Nb0.89Al0.11)(N0.84O0.16), and (Nb0.87Si0.09□0.04)(N0.87O0.13).Figure optionsDownload as PowerPoint slideHighlights
► Three Nb-oxynitrides doped either with Si, Al, Mg were bulk superconductors below ∼17 K.
► The cation vacancies induced by doping silicon act as pinning centers.
► The Si-doped sample had strong electron correlations.