THE EFFECT OF THE HEAT-TREATMENTS ON THE ANTIFERROMAGNETISM IN LA2CUO4-DELTA SINGLE-CRYSTALS

Neutron diffraction and magnetic susceptibility measurements revealed antiferromagnetic order in single crystals of La//2CuO//4 where both sublattice moments (M//s/Cu) and Neel temperatures (T//N) strongly depend on heat treatments. Deoxidization enhances M//s and T//N (M//s equals 0. 6 plus or minus 0. 05 mu //B: T//N equals 298 plus or minus 5K), whereas oxidization reduces these values (M//s equals 0. 22 plus or minus 0. 04 mu //B:T//N equals 135 plus or minus 20K) from those of as-grown crystal (M//s equals 0. 38 plus or minus 0. 05 mu //B:T//N equals 230 plus or minus 10K). A broad peak in the temperature dependence of magnetic susceptibility near T//N with the field paralell to the c-axis (a less than b less than c) is also enhanced in deoxidized crystal.