Magnetic structure of the mixed antiferromagnet NdMn0.8Fe0.2O3

Abstract

The magnetic structure of the mixed antiferromagnet NdMn0.8Fe0.2O3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k = (000) and with the magnetic structure (A(x), F-y, G(z)) for 1.6 K < T < T-N (approximate to 59 K). The Nd sublattice has a (0, f(y),0) contribution in the same temperature interval. The Mn sublattice undergoes a spin-reorientation transition at T-1 approximate to 13 K while the Nd magnetic moment abruptly increases at this temperature. Powder x-ray diffraction shows a strong magnetoelastic effect at T-N but no additional structural phase transitions from 3 to 300 K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO3 as part of our analysis. Taken together, these results show that the magnetic structure of the Mn sublattice in NdMn0.8Fe0.2O3 is a combination of the Mn and Fe parent compounds, but the magnetic ordering of the Nd sublattice spans a broader temperature interval than in the case of NdMnO3 and NdFeO3. This result is a consequence of the fact that the Nd ions do not order independently, but via polarization from the Mn/Fe sublattice.