Orthoferrite with a hidden lanthanide magnetic motif: NdFeO3

Abstract: Scrutiny of an established monoclinic magnetic space group for NdFeO3 reveals hitherto unknown properties of the orthoferrite. Future experiments using neutron and x-ray diffraction techniques can verify them. Neodymium ions possess Dirac multipoles, both time-odd (magnetic) and parity-odd (polar), that come with unique diffraction conditions. Non-magnetic polar Nd multipoles are permitted even though the monoclinic space group is centrosymmetric. Dirac multipoles are forbidden by symmetry at sites occupied by ferric ions. Available diffraction patterns have not been analysed for Dirac multipoles. Nor all permitted components of the axial dipoles and quadrupoles. In the case of neutron diffraction, magnetic quadrupoles are correlations between anapole and orbital degrees of freedom. We give conditions for the observation of Templeton-Templeton scattering of x-rays, created by angular anisotropy in the electronic charge distribution. Axial multipoles are the sole providers of dichroic signals.