  We present a study of the piezostrain-tunable gyrotropic dynamics in
Co$_{40}$Fe$_{40}$B$_{20}$ vortex microstructures fabricated on a 0.7PMN-0.3PT
single crystalline substrate. Using field-modulated spin rectification
measurements, we demonstrate large frequency tunability (up to 45 %) in
individual microdisks accessed locally with low surface voltages, and
magnetoresistive readout. With increased voltage applied to the PMN-PT, we
observe a gradual decrease of the vortex core gyrotropic frequency associated
with the strain-induced magnetoelastic energy contribution. The frequency
tunability strongly depends on the disk size, with increased frequency
downshift for the disks with larger diameter. Micromagnetic simulations suggest
that the observed size effects originate from the joint action of the
strain-induced magnetoelastic and demagnetizing energies in large magnetic
disks. These results enable a selective energy-efficient tuning of the vortex
gyrotropic frequency in individual vortex-based oscillators with all-electrical
operation.
