Electronic phase separation in lightly doped La2-xSrxCuO4 -: art. no. 134515

The hole concentration dependence of the magnetic correlations is studied in very lightly doped La2-xSrxCuO4 (x<0.02), which shows coexistence of a three-dimensional antiferromagnetic long-range-ordered phase and a spin-glass phase at low temperatures. It is found that the spin-glass phase in the coexistence region also shows a diagonal spin modulation as in the pure spin-glass phase in La2-xSrxCuO4 (0.02 <= x <= 0.055). Below x similar to 0.02 the diagonal stripe structure is the same as that in x similar to 0.02 with a volume fraction almost proportional to hole concentration, suggesting that electronic phase separation of the doped holes occurs so that some regions with hole concentration c(h)similar to 0.02 and the rest with c(h)similar to 0 are formed. To our best knowledge, this represents the most direct observation to date of electronic phase separation in lightly doped antiferromagnets. Such phase separation has been predicted by a number of theories.