Ferromagnetic Peierls insulator state in $\mathit{A}$Mg$_4$Mn$_6$O$_{15}$ ($\mathit{A}$ = K, Rb, Cs)

TL;DR

This study uses density functional theory to analyze the electronic structure of mixed-valent manganese oxides, revealing a ferromagnetic insulator state driven by Peierls distortion and double-exchange mechanisms in a cubic lattice.

Contribution

It demonstrates that these manganese oxides are ferromagnetic insulators with a Peierls-distorted structure explained by a three-dimensional chain model.

Findings

System is a fully spin-polarized ferromagnetic insulator.

Electronic structure described by 3D arrangement of 1D chains.

Peierls distortion induces insulating behavior.

Abstract

Using the density-functional-theory based electronic structure calculations, we study the electronic state of recently discovered mixed-valent manganese oxides $A$Mg$_4$Mn$_6$O$_{15}$ ($A=$ K, Rb, Cs), which are fully spin-polarized ferromagnetic insulators with a cubic crystal structure. We show that the system may be described as a three-dimensional arrangement of the one-dimensional chains of a $2p$ orbital of O and a $3d$ orbital of Mn running along the three axes of the cubic lattice. We thereby argue that in the ground state the chains are fully spin polarized due to the double-exchange mechanism and are distorted by the Peierls mechanism to make the system insulating.