Lawrence Berkeley National Laboratory

ABSTRACT The pyrochlore vanadates are compelling candidates for next‐generation dissipationless devices. and are ferromagnetic insulators ( T 70 K) that are believed to exhibit the magnon Hall effect and are expected to host topological magnons. Their completely dissipationless magnon edge states could be harnessed to realize low‐power information transport in spintronic or magnonic devices. As a crucial step in the realization of devices, we synthesize the first thin films of pyrochlore on isostructural substrates and explore the evolution of their magnetic properties down to the ultrathin limit. All films are insulating ferromagnets with transition temperatures of up to the bulk value ( T 68 K) that decrease with thickness according to finite‐size effects. Our films also exhibit a change in anisotropy from in‐plane to out‐of‐plane easy axis coincident with the development of partial strain relaxation and nonzero magnetic hysteresis in an applied field. This evolution demonstrates the impact of strain on magnetic anisotropy and paves the way to tunable magnon topology.