Mudgel, Monika and Awana, V. P. S. and Bhalla, G. L. and Kishan, H. (2008) Superconductivity of Nb(1-x) Mg (x) B(2): Impact of Stretched c-Parameter. Journal of Superconductivity and Novel Magnetism, 21 (8). 457-460 . ISSN 1557-1947

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We have performed a systematic study on the occurrence of superconductivity in Nb(1-x) Mg (x) B(2) (0.0 x n0.40). X-ray diffraction and magnetization measurements are carried out to determine the changes in lattice parameters, superconducting transition temperature (T (c) ) and critical field (H (c1)). The substitution of Mg at Nb site results in considerable stretching of c-parameter with only a slight change in a parameter. Rietveld analysis on X-ray diffraction patterns gives a=3.11 angstrom and c=3.26 angstrom for pure NbB(2) while a=3.10 angstrom and c=3.32 angstrom for Nb(0.60)Mg(0.40)B(2). This increased c-parameter introduces superconductivity in niobium diboride. Magnetization measurements though indicate the absence of superconductivity in NbB(2), the same shows a clear diamagnetic signal at about 10 K for Nb(0.60)Mg(0.40)B(2) sample. The magnetization M(H) plots exhibit weak superconductivity like hysteresis loops. The stretching of c-parameter from around 3.26 to 3.32 i.e. by 0.06 cannot be explained solely by substitution of Nb by Mg in the lattice. It seems that some Nb deficiencies are introduced in the Nb(1-x) Mg (x) B(2) as Mg is not substituted completely at the vacant Nb sites. This could be seen from XRD results, where one can clearly notice the presence of small amount of MgO in Nb(1-x) Mg (x) B(2) samples.

Item Type: Article
Subjects: Applied Physics/Condensed Matter
Depositing User: Ms Neetu Chandra
Date Deposited: 18 Apr 2017 08:45
Last Modified: 18 Apr 2017 08:45

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