SPIN-GLASS ORDERING IN NON PHASE-SEPARATED LA2CUO4.03 STUDIED BY MU-SR

Electron spin-freezing at T-f = 8 K has been detected by muon spin rot ation mu SR in a superconducting (T-c = 12 K) single crystal of La2CuO 4+y (y similar or equal to 0.03). The sample belongs to the series of La2CuO4 single crystals, which after being doped with extra oxygen, do not reveal any macroscopic structural phase separation for y less tha n or equal to 0.03, verified by X-ray and neutron diffraction. At T = 2.5 K the crystal fraction with frozen electronic moments amounts to m ore than 65% of the crystal volume. The shape and parameters of the mu on spin polarization function are typical for the Cu2+ spin-glass-like state.