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arXiv · 1802.08610

Revisiting the Magnetic Structure and Charge Ordering in La$_{1/3}$Sr$_{2/3}$FeO$_3$ by Neutron Powder Diffraction and Mössbauer Spectroscopy

F. Li·V. Pomjakushin·T. Mazet·R. Sibille·B. Malaman·R. Yadav·L. Keller·M. Medarde·K. Conder·E. Pomjakushina
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Abstract

The magnetic ordering of La$_{1/3}$Sr$_{2/3}$FeO$_3$ perovskite has been studied by neutron powder diffraction and $^{57}$Fe Mössbauer spectroscopy down to 2 K. From symmetry analysis, a chiral helical model and a collinear model are proposed to describe the magnetic structure. Both are commensurate, with propagation vector k = (0,0,1) in R-3c space group. In the former model, the magnetic moments of Fe adopt the magnetic space group P3$_{2}$21 and have helical and antiferromagnetic ordering propagating along the c axis. The model allows only one Fe site, with a magnetic moment of 3.46(2) $μ_{\rm{B}}$ at 2 K. In the latter model, the magnetic moments of iron ions adopt the magnetic space group C2/c or C2'/c' and are aligned collinearly. The model allows the presence of two inequivalent Fe sites with magnetic moments of amplitude 3.26(3) $μ_{\rm{B}}$ and 3.67(2) $μ_{\rm{B}}$, respectively. The neutron diffraction pattern is equally well fitted by either model. The Mössbauer spectroscopy study suggests a single charge state Fe$^{3.66+}$ above the magnetic transition and a charge disproportionation into Fe$^{(3.66-ζ)+}$ and Fe$^{(3.66+2ζ)+}$ below the magnetic transition. The compatibility of the magnetic structure models with the Mössbauer spectroscopy results is discussed.

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F. Li, V. Pomjakushin, T. Mazet, R. Sibille, B. Malaman, R. Yadav, L. Keller, M. Medarde, K. Conder, E. Pomjakushina. 2018-05-17. Revisiting the Magnetic Structure and Charge Ordering in La$_{1/3}$Sr$_{2/3}$FeO$_3$ by Neutron Powder Diffraction and Mössbauer Spectroscopy. https://doi.org/10.1103/physrevb.97.174417

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