Two-dimensional spin correlations and successive magnetic phase transitions inNd2CuO4

${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ is found to be a quasi-two-dimensional antiferromagnet with $T_N$=255 K. Successive phase transitions occur due to the ${\mathrm{Cu}}^{2+}$ spin reorientation as well as, at low temperatures, the participation of the ${\mathrm{Nd}}^{3+}$ spins in the three-dimensional long-range order. A sharp peak corresponding to the two-dimensional spin correlations is observed in energy-integrated scans. The magnetic properties at high temperatures are closely similar to those in ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$. .AE