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 rotation mu SR in a superconducting (T-c = 12 K) single crystal of La2CuO4+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 than 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 more than 65% of the crystal volume. The shape and parameters of the muon spin polarization function are typical for the Cu2+ spin-glass-like state.