SPIN-FREEZING IN SUPERCONDUCTING LA2CUO4.03 SINGLE-CRYSTAL

Electron spin-freezing at T-f = 8 K has been detected in superconducti ng (T-c = 12 K) single crystal La2CuO4+y (y similar or equal to 0.03) by ZF-mu SR. According to diffraction data, the crystal is in Bmab pha se without any traces of structural phase separation. TF-mu SR experim ent has shown that no Abrikosov flux line lattice is formed below T-c. The data allow us to assume that the magnetic and superconducting reg ions in the crystal are space separated on the microscopic scales simi lar to 10(2) Angstrom. The presence of large field induced broadening of the Knight shift distribution k(sigma) > 1000 ppm indicates that th e crystal contains micro-regions possessing enhanced magnetic suscepti bility.