Phase diagram of YBa$_2$Cu$_3$O$_{7-y}$ at T$<$T$_c$ based on Cu(2) transverse nuclear relaxation

Two maxima in transverse relaxation rate of Cu(2) nuclei in YBa 2 Cu 3 O 7 − y are observed, at T =35 K and T = 47 K. Comparison of the 63 Cu(2) and 65 Cu(2) rates at T = 47 K indicates the magnetic character of relaxation. The enhancement at T = 47 K of fluctuating local magnetic fields perpendicular to the CuO 2 planes is connected with the critical fluctuations of orbital currents. Maximum at T = 35 K is connected with the appearance of inhomogeneous supeconducting phase. Together with data published to date, our experimental results allow to suggest a qualitatively new phase diagram of the superconducting phase.