Synthesis and study of the crystallographic and magnetic structure of the ferrimagnetic oxideErFeMnO5

Abstract

A ferrimagnetic oxide of composition $\mathrm{Er}\mathrm{Fe}\mathrm{Mn}{\mathrm{O}}_{5}$ has been obtained by replacing half of the Mn atoms by Fe in $\mathrm{Er}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$. The crystallographic and magnetic structure have been studied by neutron powder diffraction (NPD) experiments, in complement with magnetization and susceptibility measurements. As the parent compound, $\mathrm{Er}\mathrm{Fe}\mathrm{Mn}{\mathrm{O}}_{5}$ is orthorhombic, $Pbam$ space group, and its crystal structure contains infinite chains of ${\mathrm{Mn}}^{4+}{\mathrm{O}}_{6}$ edge-sharing octahedra, linked together by ${\mathrm{Fe}}^{3+}{\mathrm{O}}_{5}$ pyramids and $\mathrm{Er}{\mathrm{O}}_{8}$ units. There is a certain antisite disorder in the structure, with a 4.6% of the ${\mathrm{Mn}}^{4+}$ positions occupied by Fe cations, and a 11.6% of the ${\mathrm{Fe}}^{3+}$ positions occupied by ${\mathrm{Mn}}^{3+}$ cations. Magnetization and NPD data demonstrate that $\mathrm{Er}\mathrm{Fe}\mathrm{Mn}{\mathrm{O}}_{5}$ undergoes long-range magnetic ordering below ${T}_{\mathrm{C}}\ensuremath{\approx}165\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The magnetic structure is defined by the propagation vector $\mathbf{k}=0$. Initially, the magnetic order only concerns the ${\mathrm{Mn}}^{4+}$ and ${\mathrm{Fe}}^{3+}$ cations, in a magnetic arrangement defined by the basis vectors $(0,0,{F}_{\mathrm{z}})$ and $(0,0,{F}_{\mathrm{z}}^{\ensuremath{'}})$, respectively. ${\mathrm{Mn}}^{4+}$ and ${\mathrm{Fe}}^{3+}$ magnetic moments are antiferromagnetically coupled, giving a global ferrimagnetic structure. The ${\mathrm{Er}}^{3+}$ sublattice becomes ordered below $75\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with a spin arrangement given by $(0,0,{F}_{\mathrm{z}}^{\ensuremath{''}})$. At $T=2.3\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the $z$ components for the magnetic moments of the ${\mathrm{Fe}}^{3+}$, ${\mathrm{Mn}}^{4+}$, and ${\mathrm{Er}}^{3+}$ cations are, respectively, $3.9(1){\ensuremath{\mu}}_{\mathrm{B}}$, $\ensuremath{-}2.4(1){\ensuremath{\mu}}_{\mathrm{B}}$, and $8.59(7){\ensuremath{\mu}}_{\mathrm{B}}$.