Pajerowski, D.; Escanhoela, C.; Haskel, D. ; Prisk, T.; Frontzek, M.; Phelan, D.; Mihalik, M.; Mihalik, M.
The orthorhombic pseudo-perovskite series NdMn1-xFexO3+δ has negative magnetization, i.e. magnetization directed opposite to an applied field under certain conditions, for x=0.2 and x=0.25. We have investigated the microscopic origin of this phenomenon for x=0.2 by using elastic and inelastic scattering techniques including neutron backscattering, X-ray magnetic circular dichroism at the Mn K and Nd L2 edges, neutron powder diffraction, and powder inelastic neutron scattering. We find that Nd3+ ions possess zero field ordered moments of 1.6 μB per ion at 1.5 K oriented parallel to the Mn moments. Based upon the neutron diffraction, there is a freezing of magnetic clusters before the long-range order sets in. The Nd crystal field levels shift with temperature due to a molecular field that is 1.1 meV at 1.5 K. These findings are consistent with a magnetic domain/cluster model for the negative magnetization in NdMn0.8Fe0.2O3+δ.