Comments on "Vortex phase diagram of HgBa$_2$Ca$_2$Cu$_3$O$_{8+δ}$ thin films from magnetoresistance measurements"

Abstract

We make comments on the paper presented by Kim \textit{et al.} [Phys. Rev. B \textbf{61}, 11317 (2000)]. The authors analyzed activation energies of HgBa$_2$Ca$_2$Cu$_3$O$_{8+δ}$ thin films with a scaling relation, and defined four vortex regions for thin films. We find that the definitions of four vortex regions and the scaling relation are questionable when studying their definition of the resistivity range for thermally activated flux flow. Using the empirical activation energy form suggested by Zhang \textit{et al.} [Phys. Rev. B \textbf{71}, 052502 (2005)] for lower resistivity data, we find that the form is not only in good agreement with the resistivity $ρ(T,H)$, but also with the apparent activation energy $-\partial \ln ρ(T,H)/\partial T^{-1}$.