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

Structural behaviour of niobium oxynitride under high pressure

“…Crystal structure of NbN 0.98 O 0.02 is cubic face centered with space group 225 (F m3m). At ambient condition, lattice parameter determined using Rietveld refinement is ~4.43Å which is consistent with earlier studies [4] .…”

Probing the superconducting properties of the Si-doped Nb-oxynitride superconductor(Nb0.87Si0.09□0.

“…superconducting transition temperature, the critical current density (J C ) for the Si-doped sample, estimated from the isothermal magnetic hysteresis, was ≈2.5 × 10 4 A/cm 2 at 5 K, nearly four times higher than the corresponding values for Mgor Al-doped samples, which was suggested to arise possibly because the cationic vacancies induced by silicon doping act as additional pinning centers in the rocksalt structure [21]. Heat capacity measurements also showed strong correlations for the Si-doped sample, as reflected by a high value of the Sommerfeld constant γ (≈25 mJ/mol K 2 ), in contrast with much lower values of γ for the Mg-doped and the Al-doped samples (0.1798 and 3 mJ/mol K 2 , respectively), where the parameter γ stands for the coefficient for the electronic contribution to the heat capacity in the equation C = γ T + βT 3 [21].…”

“…Heat capacity measurements also showed strong correlations for the Si-doped sample, as reflected by a high value of the Sommerfeld constant γ (≈25 mJ/mol K 2 ), in contrast with much lower values of γ for the Mg-doped and the Al-doped samples (0.1798 and 3 mJ/mol K 2 , respectively), where the parameter γ stands for the coefficient for the electronic contribution to the heat capacity in the equation C = γ T + βT 3 [21]. One could say that the Mg-and Al-doped samples behaved as nearly "free electron" systems.…”

Effects of manganese and nickel addition on the preparation of niobium oxynitrides

“…The estimated J C at 5 K for the Si-doped sample was ∼2.5 × 10 4 A/cm 2 under a magnetic field of 1 T and for an average grain dimension of 0.01 cm. 10 The superconducting state of (Nb 0.87 Si 0.09 0.04 )(N 0.87 O 0.13 ) was very recently studied using muon spin rotation and relaxation. The Uemura plot of the niobium oxynitride suggested that the mechanism for superconductivity may not be entirely conventional, but rather, resemble those in cuprates, organics, and heavy fermion systems.…”

“…Oxynitrides show a rich set of characteristics similar to those of the abovementioned (Nb,Si)(N,O) forming a useful nanometer-to micrometer-sized structure as a flux pinning center for superconductivity. [7][8][9][10][11] Another example of shaping at the nanoscale is gallium oxynitride nanowire formation. It has been demonstrated that anisotropic crystal growth is induced by the thermal metastability of the bonds between nitrogen and doped Co or Ni in a nitride crystal lattice.…”