  The phenomenon of ferromagnetic resonance (FMR) provides fundamental
information on the physics of magnetic materials and lies at the heart of a
variety of signal processing microwave devices. Here we demonstrate
theoretically that substrate-induced lattice strains may change the FMR
frequency of an epitaxial ferromagnetic film dramatically, leading to ultralow
and ultrahigh resonance frequencies at room temperature. Remarkably, the FMR
frequency varies with the epitaxial strain nonmonotonically, reaching minimum
at a critical strain corresponding to the strain-induced spin reorientation
transition. Furthermore, by coupling the ferromagnetic film to a ferroelectric
substrate, it becomes possible to achieve an efficient voltage control of FMR
parameters. In contrast to previous studies, we found that the tunability of
FMR frequency varies with the applied electric field and strongly increases at
critical field intensity. The revealed features open up wide opportunities for
the development of advanced tunable magnetoelectric devices based on strained
nanomagnets.
