The magnetic structure of polar $G$-type charge and orbital ordered Hg-quadruple manganite perovskites

TL;DR

This study reveals the complex magnetic structure of a novel Hg-based quadruple manganite perovskite, demonstrating unique charge, orbital, and magnetic orderings stabilized by Hg$^{2+}$ ions, using neutron diffraction and symmetry analysis.

Contribution

The paper provides the first detailed magnetic structure of Hg$_{0.7}$Na$_{0.3}$Mn$_3$Mn$_4$O$_{12}$, highlighting its unique charge and orbital orderings and the role of Hg$^{2+}$ in stabilizing these states.

Findings

Identified a G-type-like antiferromagnetic order on A' sites.

Discovered an 'up--up--down--down' AFM configuration on B sites.

Showed coupling between structural and magnetic distortions stabilizes magnetic order.

Abstract

The magnetic structure of the novel Hg$_{0.7}$Na$_{0.3}$Mn$_3$Mn$_4$O$_{12}$, a quadruple manganite perovskite that exhibits a unique $G$-type charge and orbital ordered state distinct to other $A^{2+}$Mn$_3$Mn$_4$O$_{12}$ equivalents ($A$ $=$ Ca, Sr, Cd, Pb), has been solved using powder neutron diffraction and symmetry-motivated analysis. A $G$-type-like antiferromagnetic (AFM) ordering of Mn on the $A'$ sites and a `up--up--down--down' AFM moment configuration of Mn spins on the $B$ sites is found to occur. The mechanism for the onset and stabilization of $B$ site `up--up--down--down' AFM order is explored in terms of coupling between structural and magnetic distortions. The results presented here provide evidence of the exotic charge, orbital, electronic and magnetic orderings that quadruple manganite perovskites demonstrate, and further highlighting the distinct chemistry that Hg$^{2+}$ plays in stabilizing novel states compared to other divalent $A$-site cation equivalents.