Anisotropy of the coherence length from critical currents in the   stoichiometric superconductor LiFeAs
  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. 
M. Ko\'nczykowski, C. J. van der Beek, M. A. Tanatar, V. Mosser, Yoo   Jang Song, Yong Seung Kwon and R. Prozorov
cond-mat.supr-con