The magnetic phase diagram of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ in the antiferromagnetic regime (x≤0.02) has been derived from ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ nuclear quadrupole resonance studies from 4 to 250 K. The data demonstrate freezing of the doped holes’ effective spin degrees of freedom below ${\mathit{T}}_{\mathit{f}}$≊(815 K)x into a spin-glass-like state which is superimposed on the antiferromagnetic background. These and previous results allow a detailed magnetic phase diagram to be constructed for x≤0.05 and reveal a distinct crossover at x≊0.02 in the nature of the spin-glass transition.

• Received 7 July 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.2323