Magnetic structure of NdMn${}_{0.8}$Fe${}_{0.2}$O${}_{3+\delta }$; neutron powder diffraction experiment

Abstract

The magnetic structure of the mixed antiferromagnet NdMn${}_{0.8}$Fe${}_{0.2}$O${}_3$ was resolved. Neutron powder diffraction data definitively resolve the Mn-sublattice with a magnetic propagation vector $\mathbf{k}=(000)$ and with the magnetic structure (A${}_x$, F${}_y$, G${}_z$) for 1.6~K~$<T<T_N(\approx 59$~K). The Nd-sublattice has a (0, f${}_y$, 0) contribution in the same temperature interval. The Mn sublattice undergoes spin-reorientation transition at $T_1\approx 13$~K while the Nd magnetic moment keep ordered abruptly increases at this temperature. Powder X-ray diffraction shows a strong magnetoelastic effect at $T_N$ but no additional structural phase transitions from 2~K to 300~K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO${}_3$ as part of our analysis. Taken together, these results show the magnetic structure of Mn-sublattice in NdMn${}_{0.8}$Fe${}_{0.2}$O${}_3$ is a combination of the Mn and Fe parent compounds, but the magnetic ordering of Nd sublattice spans over broader temperature interval than in case of NdMnO${}_3$ and NdFeO${}_3$. This result is a consequence of the fact that the Nd ions do not order independently, but via polarization from Mn/Fe sublattice.

arXiv commentregular article, 11 pages, 6 figures