Spin susceptibility and superexchange interaction in the antiferromagnet CuO

Experimental evidence for the quasi-one-dimensional (1D) antiferromagnetism of CuO is presented in a framework of Heisenberg model. We have obtained an experimental absolute value of the paramagnetic spin susceptibility of CuO by subtracting the orbital susceptibility separately from the total susceptibility through the ${}^{63}\mathrm{Cu}$ NMR shift measurement, and compared directly with the theoretical predictions. The result is best described by a 1D $S=\frac{1}{2}$ antiferromagnetic Heisenberg model, supporting the speculations and conclusions drawn by other methods. We also present a quantitative reason why CuO is unexpectedly a quasi-1D antiferromagnet in spite of appearing to have 3D structure.