Anomalous broadening of the spin-flop transition in the reentrant spin-glass phase of La_2-xSr_xCuO₄ (x = 0.018)

The magnetization in a lightly doped La_2-xSr_xCuO₄ (x = 0.018) single crystal was measured. Spin-flop transition was clearly observed in the hole-doped antiferromagnetically ordered state under increasing magnetic fields perpendicular to the CuO₂ plane. In the spin-glass phase below 25 K, the spin-flop transition becomes broad but the step in the magnetization curve associated with the transition remains finite at the lowest temperature. We show in this report that, at low temperature, the homogeneous antiferromagnetic order is disturbed by the redistribution of holes, and that the spatial variance of the local hole concentration around x = 0.018 increases.