  Unlike other switchable mirrors, Mg2NiHx films show large changes in
reflection that yield very low reflectance (high absorptance) at different
hydrogen contents, far before reaching the semiconducting state. The resulting
reflectance patterns are of interference origin, due to a self-organized
layered hydrogenation mechanism that starts at the substrate interface, and can
therefore be tuned by varying the film thickness. This tunability, together
with the high absorptance contrast observed between the solar and the thermal
energies, strongly suggests the use of these films in smart coatings for solar
applications.
