Summary: Scaling behavior of the critical current density in MgCNi3 microfibers
D. P. Young, M. Moldovan, and P. W. Adams
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
(Received 3 May 2004; published 20 August 2004)
We present transport critical current measurements on microfibers consisting of a 80-nm thick layer of
polycrystalline MgCNi3 synthesized directly onto 7- m diameter carbon fibers. Near the transition temperature
Tc, the critical current density Jc is well described by the power law form 1- T/Tc
, where =2 with no
crossover to the Ginzburg-Landau exponent =1.5. We extrapolate Jc 0 4 107
, 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 =Jc 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.
DOI: 10.1103/PhysRevB.70.064508 PACS number(s): 74.25.Sv, 74.70.Ad, 74.78.Na
The only known superconducting nonoxide perovskite
MgCNi3 has come under intense study since its discovery