Scaling behavior of the critical current density in MgCNi3 microfibers

D. P. Young, Louisiana State University
M. Moldovan, Louisiana State University
P. W. Adams, Louisiana State University


We present transport critical current measurements on microfibers consisting of a 80-nm thick layer of polycrystalline MgCNi3 synthesized directly onto 7-μm diameter carbon fibers. Near the transition temperature Tc, the critical current density Jc is well described by the power law form [1 -(T/Tc)2] α, where α = 2 with no crossover to the Ginzburg-Landau exponent α = 1.5. We extrapolate Jc(0) ≈ 4 × 10 7 A/cm2, which is an order of magnitude greater than estimates obtained from magnetization measurements of polycrystalline powders. The field dependence is purely exponential Jc(T,H)=J c(T)exp(-H/H0) over the entire field range of 0 to 9 T. The unconventional scaling behavior of the critical current may be rooted in an anomalous temperature dependence of the London penetration depth.