# Intrinsic Ferromagnetism in Electrenes

## TL;DR

This paper demonstrates intrinsic ferromagnetism in monolayer electrides, where excess electrons act as anions, leading to a new mechanism for 2D magnetism distinct from traditional d-orbital-based ferromagnetism.

## Contribution

It reveals that magnetism in electrenes originates from anionic electrons, introducing a novel mechanism for intrinsic 2D ferromagnetism without magnetic elements.

## Key findings

- Curie temperature of 235 K achieved
- Long-range ferromagnetic interaction mediated by electron wave functions
- Magnetism driven by localized excess electrons at the hexagon center

## Abstract

We report intrinsic ferromagnetism in monolayer electrides or electrenes, in which excess electrons act as anions. Our first-principles calculations demonstrate that magnetism in such electron-rich two-dimensional (2D) materials originates from the anionic electrons rather than partially filled d orbitals, which is fundamentally different from ferromagnetism found in other 2D intrinsic magnetic materials. Taking the honeycomb LaBr$_2$ (La$^{3+}$Br$^{-}_{2}\cdot e^{-}$) as an example, our calculations reveal that the excess electron is localized at the center of the hexagon, which leads to strong Stoner-instability of the associated states at the Fermi energy, resulting in spontaneous magnetization and formation of a local moment. The overlap of extended tails of the wave functions of these electrons mediates a long-range ferromagnetic interaction, contributing to a Curie temperature ($T_\textrm{c}$) of 235 K and a coercive field ($H_\textrm{c}$) of 0.53 T, which can be further enhanced by hole doping. The dual nature, localization and extension, of the electronic states suggests a unique mechanism in such magnetic-element-free electrenes as intrinsic 2D ferromagnets.