ESR studies of doped La2CuO4

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