Oxidation tuning of ferroic transitions in Gd2C monolayer

Tuning of ferroic phases provides great opportunities for material functionalities, especially in two-dimensional materials. Here, a 4f rare-earth carbide Gd2C monolayer is predicted to be a ferromagnetic metal with large magnetization, inherited from its bulk property. Based on first-principles calculations, we propose a strategy that the surface passivation can effectively tune its ferroicity, namely, switching among ferromagnetic, antiferromagnetic, and ferroelectric phases. Metal–insulator transition also occurs accompanying these ferroic transitions. Our calculation also suggests that the magneto-optic Kerr effect and second harmonic generation are effective methods in monitoring these phase transitions.