Singh, K. P. and Awana, V. P. S. and Balamurugan, S. and Shahabuddin, M. and Singh, H. K. and Husain, M. and Bauminger, E. R. and Felner , I. (2008) Nano Fe3O4 Induced Fluxoid Jumps and Low Field Enhanced Critical Current Density in MgB2 Superconductor. Journal of Superconductivity and Novel Magnetism, 21 (1). pp. 39-44. ISSN 1557-1947

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Nano particle of Fe3O4 (nFe3O4) up to 6 at% were doped in the superconducting MgB2 samples. Despite the strong ferromagnetic nature of Fe3O4, both the ac susceptibility and the resistivity measurements show that up to 4 at% of Fe3O4, T c =38 K is not changed, whereas for 6% T c decreases by 6 K. This indicates that a low concentration of Fe does not substitute either the Mg or B sites and probably occupies the intergrain spaces. For 0.5% doped Fe3O4, an increase in J c with respect to the pure MgB2 samples is observed in the lower field and temperature regions (H<2 T and 20 K) indicating an enhanced flux pinning and the magnetic activation, i.e., the interaction between the magnetic dipole of Fe ion and the vortices is weak in comparison to the effective pinning potential. Whereas, at H>2 T, J c of the doped samples is always less than that of MgB2, and the activation is dominant in comparison with the effective pinning potential provided by the doping. Flux jumps are observed in lower T and H regions for the samples doped up to 1% nFe3O4 only. Magnetization plots of higher Fe content samples exhibited clear paramagnetic background. Mossbauer measurements for the higher (4, 6 at%) nFe3O4 doped MgB2 samples show that at RT, the hyperfine field for both samples is ∼100 kOe and ∼120 kOe at 90 K. This means that the nFe3O4 particles decompose and form possibly an intermetallic Fe-B phase in the matrix.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s Springer Verlag.
Subjects: Physics
Depositing User: Ms Neetu Chandra
Date Deposited: 20 Apr 2015 07:30
Last Modified: 20 Apr 2015 07:30

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