Room temperature multiferroism in CaTcO${}_3$ by interface engineering

The structural instabilities of ATcO${}_3$(A= Ca, Sr, Ba) are investigated by first-principles calculations. In addiction to the large octahedral rotation instability, a weak ferroelectric tendency is identified in CaTcO${}_3$. We show that the ferroelectricity in CaTcO${}_3$ can be recovered by interface engineering based on CaTcO${}_3$/BaTcO${}_3$ superlattices, where the octahedral rotation is largely suppressed. The N{'e}el temperature is found to be $\sim$ 816 K, indicating that CaTcO${}_3$ can be engineered into a new room temperature multiferroic material.