Antiferromagnetism and oxygen deficiency in single-crystal La2CuO4- delta.

Two single crystals of undoped La/sub 2/CuO/sub 4/ are studied by neutron diffraction between T = 5 and 300 K. In one crystal oxygen vacancies are created by heat treatment and the magnetic properties are found to depend strongly on this treatment. While the untreated sample is found to order antiferromagnetically at T/sub N/approx. =50 K, the heat-treated crystal orders at T/sub N/approx. =150 K with a somewhat larger moment. The magnetic structure is the same for the two crystals and supports previously reported powder results.