Particularly large rare earths such as Nd, Pr, and Dy are important for magnets in wind turbine generators and electric vehicles. Furthermore, the chemical similarity between the different rare earths also makes their isolation and purification expensive as they are usually found together in the same ore. The tolerance factor of hexagonal manganites will benefit from using smaller, and cheaper, rare earth cations such as Er and Y, which combined with larger cations such as Gd, Ce and La, which are also comparatively cheaper. This could allow comparatively affordable materials with excellent OSC and oxidation kinetics. High entropy alloys also have a high tolerance for impurities, enabling the use of scrap metals or recycled materials for synthesis, 1 and this likely applies to high entropy oxides as well.