A Minimal tight-binding model for ferromagnetic canted bilayer manganites

TL;DR

This paper develops a minimal tight-binding model to accurately describe the electronic band structure of ferromagnetic and antiferromagnetic bilayer manganites, capturing key features like bilayer splitting and orbital mixing.

Contribution

It introduces a robust, minimal tight-binding model that incorporates bilayer coupling, orbital mixing, and $k_z$ dispersion for bilayer manganites, advancing understanding of their electronic structure.

Findings

The model captures bilayer splitting effects.

Orbital mixing significantly influences electronic behavior.

Inclusion of $k_z$ dispersion improves accuracy.

Abstract

Half-metallicity in materials has been a subject of extensive research due to its potential for applications in spintronics. Ferromagnetic manganites have been seen as a good candidate, and aside from a small minority-spin pocket observed in La$_{2-2x}$Sr$_{1+2x}$Mn$_{2}$O$_{7}$ $(x=0.38)$, transport measurements show that ferromagnetic manganites essentially behave like half metals. Here we develop robust tight-binding models to describe the electronic band structure of the majority as well as minority spin states of ferromagnetic, spin-canted antiferromagnetic, and fully antiferromagnetic bilayer manganites. Both the bilayer coupling between the MnO$_2$ planes and the mixing of the $|x^2 - y^2>$ and $|3z^2 - r^2>$ Mn 3d orbitals play an important role in the subtle behavior of the bilayer splitting. Effects of $k_z$ dispersion are included.