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首页> 外文期刊>Journal of Superconductivity and Novel Magnetism >Nano Fe3O4 Induced Fluxoid Jumps and Low Field Enhanced Critical Current Density in MgB2 Superconductor
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Nano Fe3O4 Induced Fluxoid Jumps and Low Field Enhanced Critical Current Density in MgB2 Superconductor

机译：纳米Fe3 O4 引起的MgB2 超导体中的磁通跃迁和低场增强的临界电流密度

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摘要

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.
机译：在超导MgB2 样品中掺杂了高达6 at％的Fe3 O4 （nFe3 O4 ）纳米颗粒。尽管Fe3 O4 具有很强的铁磁性质，但其磁化率和电阻率测量结果均显示，高达4 at％的Fe3 O4 ，T c = 38 K不变，而6％的T c 降低6K。这表明低浓度的Fe不能替代Mg或B位，并且可能占据晶间空间。对于掺杂0.5％的Fe3 O4 ，在较低的磁场和温度区域（H <2 T和与有效钉扎电势相比，图20K）表明磁通钉扎和磁激活增强，即，Fe离子的磁偶极子与涡旋之间的相互作用较弱。然而，在H> 2 T时，掺杂样品的J c始终小于MgB2 ，并且与掺杂提供的有效钉扎电势相比，活化作用占主导地位。仅掺杂了1％nFe3 O4 的样品在较低的T和H区域观察到通量跳跃。高铁含量样品的磁化曲线显示出清晰的顺磁性背景。较高（4、6 at％）nFe3 O4 掺杂的MgB2 样品的Mossbauer测量显示，在室温下，两个样品的超精细场均为90〜100 kOe和120〜120 kOe。 K。这意味着nFe3 O4 粒子分解并可能在基体中形成金属间Fe-B相。

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

  • 作者单位

    National Physical Laboratory Dr. K.S. Krishnan Marg New Delhi 110012 India;

    National Physical Laboratory Dr. K.S. Krishnan Marg New Delhi 110012 India;

    Superconducting Materials Center NIMS 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan;

    Physics Department Jamia Millia Islamia University New Delhi 110025 India;

    National Physical Laboratory Dr. K.S. Krishnan Marg New Delhi 110012 India;

    Physics Department Jamia Millia Islamia University New Delhi 110025 India;

    National Physical Laboratory Dr. K.S. Krishnan Marg New Delhi 110012 India;

    Racah Institute of Physics Hebrew University of Jerusalem Jerusalem 91904 Israel;

    Racah Institute of Physics Hebrew University of Jerusalem Jerusalem 91904 Israel;

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  • 正文语种 eng
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  • 关键词

    MgB2; Vacuum synthesis; Nano-Fe3O4; Critical current density;

    机译：MgB2;真空合成;纳米Fe3O4;临界电流密度;

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