The anisotropic vortex transport properties of c-axis-oriented ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{4\mathrm{-}\mathit{x}}$ superconducting epitaxial films are found consistent with a dislocation-mediated second-order vortex-solid melting transition. The anisotropic critical exponents and the electronic mass ratio are determined from the scaling of the current-voltage characteristics. The nucleation energy of vortex dislocations due to both thermal and disorder fluctuations and its relation to the vortex elastic moduli is inferred from our experiments.

• Received 12 August 1991

DOI:https://doi.org/10.1103/PhysRevB.45.5710