engleski

Effect of magnetic NiCoB nanoparticles on superconductivity in MgB2 wires

A systematic study of the influence of doping MgB2 with single domain magnetic nanoparticles of NiCoB alloy, uncoated and coated with SiO2, has been performed. Electrical resistivity, transport critical current density, Jc(B, T), and magnetization of well characterized undoped and doped with 1.38 and 2.67 wt% of NiCoB particles (both uncoated and coated) MgB2 wires have been investigated in the temperature interval 2–300 K and in magnetic field B ≤ 16T. The superconducting transition temperature, Tc, decreases approximately linearly with the amount of dopand and the intergranular connectivity (the active cross-sectional area fraction, AF) is also reduced upon doping. Reduction of critical fields (irreversibility field, Birr, and upper critical field, Bc2) of doped wires was observed in the whole temperature interval, but an enhancement of Jc of doped wires with respect to the undoped one was observed at low temperature (5 K). Common scaling of Jc(B, T) curves, Birr(T) and volume pinning force, Fp, for doped and undoped wires indicates that the main mechanism of flux pinning is the same in both types of samples.

MgB2/Fe wires ; magnetic nanoparticle doping ; transport properties ; magnetic pinning

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