In high-quality $c$-axis-oriented ${\mathrm{MgB}}_2$ thin films, we observed high critical current densities ( $J_c$) of $\sim 16\mathrm{MA}/{\mathrm{cm}}^2$ at 15 K under self-fields comparable to those of cuprate high-temperature superconductors. The extrapolated value of $J_c$ at 5 K was estimated to be $\sim 40\mathrm{MA}/{\mathrm{cm}}^2$. For a magnetic field of 5 T, a $J_c$ of $\sim 0.1\mathrm{MA}/{\mathrm{cm}}^2$ was detected at 15 K, suggesting that this compound would be a very promising candidate for practical applications at high temperature and lower power consumption. The vortex-glass phase is considered to be a possible explanation for the observed high current-carrying capability.

• Received 18 May 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.087002