Emergence of strong room-temperature ferroelectricity and multiferroicity in 2D-Ti$_3$C$_2$T$_x$ free-standing MXene film

TL;DR

This study demonstrates the emergence of room-temperature ferroelectricity and multiferroicity in 2D Ti3C2Tx MXene films, revealing their potential for advanced electric and magnetic data storage applications.

Contribution

First report of ferroelectric and multiferroic phases in 2D MXene films at room temperature, achieved through a simple synthesis and air exposure process.

Findings

Room-temperature ferroelectric hysteresis observed.

Magnetic hysteresis indicating ferromagnetic coupling.

Switchable polarization under magnetic field demonstrated.

Abstract

Two-dimensional (2D) multiferroics are key candidate materials towards advancement of smart technology. Here, we employed a simple synthesis approach to address the long-awaited dream of developing ferroelectric and multiferroic 2D materials, specially in the new class of materials called MXenes. The etched Ti$_3$C$_2$T$_x$ MXene was first synthesized after HF-treatment followed by delamination process for successful synthesis of free-standing Ti$_3$C$_2$T$_x$ film. The free-standing film was then exposed to air at room-temperature as well as heated at different temperature to form TiO$_2$ layer derived from the Ti$_3$C$_2$T$_x$ MXene itself. TiO$_2$ is reported to be an incipient ferroelectric that assumes a ferroelectric phase in composite form. The structural and morphological analysis confirmed successful synthesis of free-standing film and the Raman spectroscopy revealed the formation of different phases of TiO$_2$. The ferroelectric measurement showed a clear polarization hysteresis loop at room-temperature. Also, the magnetic hysteresis was observed in the film indicating a possibility of coupling between ferroelectric and ferromagnetic phases at room-temperature. The magnetoelectric coupling test was also performed that showed a clear, switchable spontaneous polarization under applied magnetic field. This is the first report on existence of ferroelectric phase and multiferroic coupling in 2D free-standing MXene film at room-temperature which opens-up possibility of 2D materials-based electric and magnetic data storage applications at room-temperature.