Record-large magnetically driven polarization in room temperature ferromagnets Os$X_2$ monolayers

TL;DR

This paper predicts that OsX2 monolayers are ferroelectric and ferromagnetic above room temperature, exhibiting record-large magnetically induced polarization and strong magnetoelectric effects, advancing multiferroic material applications.

Contribution

It introduces a new family of 2D OsX2 monolayers with room-temperature multiferroicity and record-large magnetically induced polarization, addressing previous limitations of multiferroic materials.

Findings

Record-large magnetically induced polarization of 5.9 μC/cm².

Ferroelectricity and ferromagnetism above room temperature.

Magnetoelectric control of polarization demonstrated.

Abstract

Magnetically induced ferroelectrics in multiferroics provide an optimal approach to pursuit intrinsically strong magnetoelectricity. However, the complex antiferromagnetism, faint magnetically induced polarization, and low working temperatures make their magnetoelectric performance incompetent from the applications demands. Here, a family of two-dimensional $5d$ halides Os$X_2$ monolayers is predicted to be ferroelectric and ferromagnetic above room temperature. More interestingly, benefiting from the strong spin-orbital coupling and high-spin state of Os$^{2+}$ ion, the magnetically induced ferroelectric polarization can reach $5.9$ $\mu$C/cm$^2$, a record-large value in type-II multiferroics. The magnetoelectric effect, that is, controlling ferroelectric polarization by magnetic field has been demonstrated, and magnetically driven ferrovalley also emerges in this system. This work provides an effective way to solve the main defects of type-II multiferroics.