NonGinsburgLandau Critical Current Behavior in MgCNi_3
Abstract
We present transport critical current measurements on microfibers consisting of an 80nm thick layer of polycrystalline MgCNi_{3} synthesized directly onto 7μm diameter carbon fibers. Near the transition temperature, T_c, the critical current density, J_c, is well described by the power law form [1(T/T_c)^2]^α, where α = 2 with no crossover to the GinsburgLandau exponent α = 1.5. We extrapolate J_c(0) ∼ 4 × 10^7 A/cm^2, which is an order of magnitude larger than estimates obtained from magnetization measurements on polycrystalline powders. The field dependence is purely exponential, as J_c(T,H) = J_c(T)exp^(H/H_o) over the entire field range from 0 to 9 T. The unconventional scaling behavior of the critical current appears rooted in an anomalous temperature dependence of the London penetration depth, suggesting an unusual superconducting ground state in MgCNi_3.
 Publication:

APS March Meeting Abstracts
 Pub Date:
 March 2004
 Bibcode:
 2004APS..MARH12010Y