Specific heat of Zn-doped YBa 2 Cu 3 O 6.95 : Possible evidence for Kondo screening in the superconducting state

The magnetic field dependence of the specific heat of Zn-doped single crystals of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.95}$ was measured between 2 and 10 K and up to 8 T. Doping levels of 0, 0.15%, 0.31%, and 1% were studied and compared. In particular we searched for the Schottky anomaly associated with the Zn-induced magnetic moments.