Magnetic susceptibility anisotropy and low-dimensional antiferromagnetism of CuO

摘要

The anisotropy of the magnetic susceptibility χ and the influence of oxygen vacancies in CuO single crystals on it are investigated. The temperature dependences of χ(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 σ(H) above and below the Neel temperature T_N are plotted for a crystal before and after heat treatment. The τ(T) curves have the form characteristic of low-dimensional systems, which become three-dimensional when the temperature is lowered. The character of the χ(T) curves remains unchanged after annealing. Oxygen vacancies have practically no influence on the α-axis magnetic susceptibility, but they alter the absolute values of the b- 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 χ and an increase in the minimum value of χ. The results of the calculations of the exchange parameter I/k and the g factor are discussed in terms of the Heisenberg and Ising models for a one-dimensional system.