Transport Critical Current Densities and $n$ -Values of Multifilamentary $\hbox{MgB}_{2}$ Wires at Various Temperatures and Magnetic Fields

A series of high-performing continuous-tube-filling-forming-fabricated (CTFF) powder-in-tube-type (PIT) MgB
₂
strands have been prepared, with critical current densities, J
_c
s, higher than 1.30×10
⁵
A/cm
²
and n-values above 30 at 4.2 K, 5 T. The transport J
_c
s and corresponding n-values of a selected sample C1 were reported at temperatures, T, of 4.2-30 K and magnetic fields, B, of 0-12 T. The J
_c
- B data were fitted by Eisterer's percolation model and the temperature dependences of the fitting parameters were analyzed. The n - J
_c
curves showed a power law relationship n∞J
_c
^m
, also previously observed in state-of-the-art monocore MgB
₂
wires. Further analysis revealed that, like monofilamentary wires, the n(B, T) of this multifilamentary strand can also be estimated for all B and T based on the results of transport voltage-current (V- I) measurements made at one arbitrarily chosen temperature.