ON THE MAGNETIC-ANISOTROPY OF CUO

The anisotropy of the magnetic susceptibility of CuO has been measured. In both, the paramagnetic and the antiferromagnetic state the susceptibility can be described to a good approximation by chi = chi-a.cos2-alpha + chi-b.cos2-beta + chi-c.cos2-gamma where chi-a, chi-b and chi-c are the chi-values along the crystallographic a, b and c axes respectively and alpha, beta, gamma are the angles of the magnetic field direction with respect to these axes. At T(N2) = 212 K a positive jump in chi is observed for B0 parallel to the crystallographic b-axis and a negative jump (with increasing temperature) for B0 parallel to the c-axis, but no effect at all is observed for fields along the a-axis. It is argued that CuO behaves like a low dimensional antiferromagnet due to strong magnetic interactions along the a-direction. For T --> O the parallel susceptibility e.g. chi-b remains finite, indicating that the copper moments include appreciable orbital contributions.