Engineering Multifunctional Response in Monolayer Fe3O4 via Zr Adsorption: From Half-Metallicity to Enhanced Piezoelectricity

TL;DR

This study uses first-principles calculations to show how Zr adsorption on monolayer Fe3O4 modifies its electronic, magnetic, optical, and piezoelectric properties, enabling multifunctional tuning for advanced 2D material applications.

Contribution

It reveals how Zr adsorption at different sites significantly enhances piezoelectric and optical properties of monolayer Fe3O4, providing a new approach to multifunctional 2D material design.

Findings

Zr adsorption reduces bandgap and increases optical absorption.

Bridge site Zr greatly enhances piezoelectric coefficients.

Functionalization causes elastic softening and shifts in plasmon resonance.

Abstract

Two-dimensional (2D) magnetic oxides are increasingly studied for their multifunctional potential in fields like spintronics, optoelectronics, and energy conversion. In this research, we conduct a detailed first-principles study of pure monolayer Fe3O4 and its modification through Zr adsorption at two sites: on top of an Fe atom and at the bridge between Fe atoms. Using spin-polarized density functional theory with the GGA plus U method, we examine how adsorption affects structure, electronic, magnetic, optical, elastic, and piezoelectric properties. The original monolayer shows half-metallicity, strong spin polarization, and a moderate in-plane piezoelectric effect. Zr adsorption causes local lattice distortions and orbital hybridization, resulting in intermediate electronic states, a reduced bandgap, and increased optical absorption in both spin channels. Notably, Zr at the bridge site greatly enhances dielectric response, optical conductivity, and piezoelectric coefficients, tripling e11 compared to the pristine layer. Elastic constants indicate mechanical softening after functionalization, and energy loss spectra display shifts in plasmon resonance. These findings suggest Zr adsorption offers a controllable, non-destructive way to tune spin, charge, and lattice interactions in Fe4O4 monolayers, connecting magnetic, optical, and piezoelectric functionalities within a single 2D material platform.