Magnetic susceptibility anisotropy and low-dimensional antiferromagnetism of CuO

The anisotropy of the magnetic susceptibility chi and the influence of oxygen vacancies in CuO single crystals on it are investigated. The temperature dependences of chi(T) along the a, b, and c axes in the range 60<T<600 K and the behavior of the field dependence of the magnetization sigma(H) above and below the Neel temperature T-N are plotted for a crystal before and after heat treatment. The chi(T) curves have the form characteristic of low-dimensional systems, which become three-dimensional when the temperature is lowered. The character of the chi(T) curves remains unchanged after annealing. Oxygen vacancies have practically no influence on the a-axis magnetic susceptibility, but they alter the absolute values of the 6-and c-axis susceptibilities. The significant effects of reducing the oxygen concentration include a decrease in the magnitude of the low-temperature anomaly (increase) in chi and an increase in the minimum value of chi. The results of the calculations of the exchange parameter Ilk and the g factor are discussed in terms of the Heisenberg and Ising models for a one-dimensional system. (C) 1998 American Institute of Physics. [S1063-7761(98)01903-9].