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arXiv · 1407.1417

Spin reorientation in Na-doped BaFe$_2$As$_2$ studied by neutron diffraction

F. Wasser·A. Schneidewind·Y. Sidis·S. Aswartham·S. Wurmehl·B. Buchner·M. Braden
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Abstract

We have studied the magnetic ordering in Na doped BaFe$_2$As$_2$ by unpolarized and polarized neutron diffraction using single crystals. Unlike previously studied FeAs-based compounds that magnetically order, Ba$_{1-x}$Na$_x$Fe$_2$As$_2$ exhibits two successive magnetic transitions: For x=0.35 upon cooling magnetic order occurs at $\sim$70\ K with in-plane magnetic moments being arranged as in pure or Ni, Co and K-doped BaFe$_2$As$_2$ samples. At a temperature of $\sim$46\ K a second phase transition occurs, which the single-crystal neutron diffraction experiments can unambiguously identify as a spin reorientation. At low temperatures, the ordered magnetic moments in Ba$_{0.65}$Na$_{0.35}$Fe$_2$As$_2$ point along the $c$ direction. Magnetic correlations in these materials cannot be considered as Ising like, and spin-orbit coupling must be included in a quantitative theory.

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F. Wasser, A. Schneidewind, Y. Sidis, S. Aswartham, S. Wurmehl, B. Buchner, M. Braden. 2014-07-05. Spin reorientation in Na-doped BaFe$_2$As$_2$ studied by neutron diffraction. https://doi.org/10.1103/physrevb.91.060505

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