Electric field tuning of magnetic properties in FeGa films on ferroelastic Pb(Zr,Ti)O$_{3}$ thin films probed by ferromagnetic resonance

In order to investigate the possibility of fabricating electric field tunable thin film magnetic devices using a multiferroic transduction effect, we have patterned Fe$_{0.7}$Ga$_{0.3}$ (FeGa) films sputter-deposited on PbZr$_{0.3}$Ti$_{0.7}$O$_{3}$ (PZT(30/70))/PbZr$_{0.7}$Ti$_{0.3}$O$_{3}$ (PZT(70/30)) tetragonal/rhombohedral bilayers on Pt/Ti/SiO$_{2}$/Si wafers. Previous piezoforce microscopy studies have shown that the PZT bilayers exhibit presence of ferroelastic domains where the fraction of the local $c$/$a$ domain ratio can be tuned by an applied electric field. The FeGa top layer was patterned into 20 $\mu $m x 20 $\mu $m capacitor devices in order to apply electric field to the multilayers, and ferromagnetic resonance (FMR) measurements at 9.2 GHz were performed. Typically, a relatively sharp FMR signal observed before application of the electric field would get substantially broadened after initial application of +4 kV/cm. Angular dependent FMR indicates that magnetic anisotropy in the FeGa is indeed affected by application of electric field.