  AlN-based alloys find widespread application in high-power microelectronics,
optoelectronics, and electromechanics. The realization of ferroelectricity in
wurtzite AlN-based heterostructural alloys has opened up the possibility of
directly integrating ferroelectrics with conventional microelectronics based on
tetrahedral semiconductors such as Si, SiC and III-Vs, enabling
compute-in-memory architectures, high-density data storage, and more. The
discovery of AlN-based wurtzite ferroelectrics has been driven to date by
chemical intuition and empirical explorations. Here, we demonstrate the
computationally-guided discovery and experimental demonstration of new
ferroelectric wurtzite Al$_{1-x}$Gd$_x$N alloys. First-principles calculations
indicate that the minimum energy pathway for switching changes from a
collective to an individual switching process with a lower overall energy
barrier, at a rare-earth fraction $x$ of $x>$ 0.10$-$0.15. Experimentally,
ferroelectric switching is observed at room temperature in Al$_{1-x}$Gd$_x$N
films with $x>$ 0.12, which strongly supports the switching mechanisms in
wurtzite ferroelectrics proposed previously (Lee et al., $\textit{Science
Advances}$ 10, eadl0848, 2024). This is also the first demonstration of
ferroelectricity in an AlN-based alloy with a magnetic rare-earth element,
which could pave the way for additional functionalities such as multiferroicity
and opto-ferroelectricity in this exciting class of AlN-based materials.
