Nano Fe 3O 4 induced fluxoid jumps and low field enhanced critical current density in MgB 2 superconductor

K. P. Singh, V. P.S. Awana*, S. Balamurugan, M. Shahabuddin, H. K. Singh, M. Husain, H. Kishan, E. R. Bauminger, I. Felner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Nano particle of Fe 3O 4 (nFe 3O 4) up to 6 at% were doped in the superconducting MgB 2 samples. Despite the strong ferromagnetic nature of Fe 3O 4, both the ac susceptibility and the resistivity measurements show that up to 4 at% of Fe 3O 4, 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 Fe 3O 4, an increase in J c with respect to the pure MgB 2 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 MgB 2, 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% nFe 3O 4 only. Magnetization plots of higher Fe content samples exhibited clear paramagnetic background. Mossbauer measurements for the higher (4, 6 at%) nFe 3O 4 doped MgB 2 samples show that at RT, the hyperfine field for both samples is 100 kOe and 120 kOe at 90 K. This means that the nFe 3O 4 particles decompose and form possibly an intermetallic Fe-B phase in the matrix.

Original languageEnglish
Pages (from-to)39-44
Number of pages6
JournalJournal of Superconductivity and Novel Magnetism
Volume21
Issue number1
DOIs
StatePublished - Jan 2008

Keywords

  • Critical current density
  • MgB
  • Nano-Fe O
  • Vacuum synthesis

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