Multiferroic nitride perovskites with giant polarizations and large magnetic moments

TL;DR

This paper proposes nitride perovskites as multiferroics with large polarizations and magnetic moments, revealing multiple ferroelectric origins and potential for high-performance multiferroic materials.

Contribution

It introduces a new family of nitride perovskites with unconventional ferroelectric mechanisms and demonstrates their promising physical properties through first-principles calculations.

Findings

GdWN3 has large polarization and magnetic moment.

Ferroelectricity arises from multiple ion contributions.

Smaller rare earth ions enhance ferroelectric instability.

Abstract

Multiferroics with coupling between ferroelectricity and magnetism have been pursued for decades. However, their magnetoelectric performances remain limited due to the common trade-off between ferroelectricity and magnetism. Here, a family of nitride perovskites is proposed as multiferroics with prominent physical properties and nontrivial mechanisms. Taking GdWN$_3$ as a prototype, our first-principles calculations found that its perovskite phases own large polarizations (e.g. $111.3$ $\mu$C/cm$^2$ for the $R3c$ phase) and a magnetic moment $7$ $\mu_{\rm B}$/Gd$^{3+}$. More interestingly, its ferroelectric origin is multiple, with significant contributions from both Gd$^{3+}$ and W$^{6+}$ ions, different from its sister member LaWN$_3$ in which the ferroelectricity almost arises from W$^{6+}$ ions only. With decreasing size of rare earth ions, the A site ions would contribute more and more to the ferroelectric instability. Considering that small rare earth ions can be primary origins of both proper ferroelectricity and magnetism in nitride perovskites, our work provides a route to pursuit more multiferroics with unconventional mechanisms and optimal performances.