low-temperature magnetic structure of mno: a high-resolution neutron-diffraction study

The antiferromagnetic structure of MnO was studied using high-resolution neutron diffraction from a polycrystalline sample at 8 K. The "allowed-reflection rule" which is obeyed by the observed reflection was deduced. By use of this rule, and without recourse to calculation of intensities, it is shown unambiguously that the magnetic structure is collinear, and the magnetic configuration is deduced. By using the (115)-to-(333) magnetic intensity ratio (whose splitting is observable only with high resolution), we found that within our experimental resolution, the spin axis is perpendicular to the unique [111] direction.