ESR studies of doped La2CuO4

ESR of Gd spin probes in La2-x-yEuySrxCuO4 has been employed to study the Cu spin dynamics and its relation to stripe order of spins and charges in the low temperature tetragonal phase of this compound. In the magnetically ordered hole doped samples (0 < x less than or equal to 0.02) a strong enhancement of magnetic fluctuations on the ESR frequency scale is observed in this structural phase. At larger hole dopings (0.08 less than or equal to x less than or similar to 0.17) a drastic decrease of the Cu spin fluctuation frequency, competing with bulk superconductivity, is apparent. For the elevated hole concentrations the obtained results are consistent with the stripe model, whereas in the low hole doping regime the data give no evidence for the stripe phase formation.