  Miniature Hall-probe arrays were used to measure the critical current
densities for the three main directions of vortex motion in the stoichiometric
LiFeAs superconductor. These correspond to vortices oriented along the c-axis
moving parallel to the ab-plane, and to vortices in the ab-plane moving
perpendicular to, and within the plane, respectively. The measurements were
carried out in the low-field regime of strong vortex pinning, in which the
critical current anisotropy is solely determined by the coherence length
anisotropy parameter, {\epsilon}_{\xi}. This allows extraction of
{\epsilon}_{\xi} at magnetic fields far below the upper critical field B_c2. We
find that increasing magnetic field decreases the anisotropy of the coherence
length.
