Magnetic structure of CuO by neutron diffraction with polarization analysis

Abstract

Neutron diffraction with polarization analysis was performed on a single crystal of CuO, oriented with its alpha * and c* axes in the diffraction plane. It was verified that in the commensurate phase I(0-212.7 K; k=(1/2, 0, -1/2)), the magnetic moments were indeed along b*, but it was found that in the incommensurate phase II (212.7-232.5 K; k=(0.506, 0, -0.483)) there also exists a component of the magnetic moment along b* in disagreement with an earlier study by Forsyth et al. (1988). The data are in agreement with the very recent results of Brown et al. (1991). The authors propose a helimagnetic arrangement in the incommensurate phase II, with the magnetic moments rotating in the plane (b*; 0.506 alpha *+1.517c*). They present a short account of their experimental results, a study of the stability of the magnetic structure in phase II and the symmetry analysis of the possible magnetic space groups.