We present the results of magnetic-susceptibility, heat-capacity, electrical-resistivity, and thermoelectric-power measurements on ${\mathrm{La}}_2\mathrm{Cu}{\mathrm{O}}_{4-y}$. The crystallographic, magnetic, and electronic transport properties are found to be extremely sensitive to the oxygen-defect concentration $y$. Coupled with x-ray and neutron-diffraction data presented in a companion paper, we find that long-range antiferromagnetic order develops with increasing $y$ out of a nonmagnetic ground state at $y\simeq 0$ into a state with a maximum Néel temperature of 290 K at $y\simeq 0.03$.

• Received 20 May 1987

DOI:https://doi.org/10.1103/PhysRevB.36.4007