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 t emperature dependences of chi(T) along the a, b, and c axes in the ran ge 60<T<600 K and the behavior of the field dependence of the magnetiz ation sigma(H) above and below the Neel temperature T-N are plotted fo r a crystal before and after heat treatment. The chi(T) curves have th e form characteristic of low-dimensional systems, which become three-d imensional when the temperature is lowered. The character of the chi(T ) curves remains unchanged after annealing. Oxygen vacancies have prac tically no influence on the a-axis magnetic susceptibility, but they a lter the absolute values of the 6-and c-axis susceptibilities. The sig nificant effects of reducing the oxygen concentration include a decrea se in the magnitude of the low-temperature anomaly (increase) in chi a nd an increase in the minimum value of chi. The results of the calcula tions 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].