Microwave Response of BiFeO3 Films in Parallel-Plate Capacitors

Dielectric response of the BiFeO3 films in a parallel-plate capacitor configuration is studied in the frequency range 1 MHz-30 GHz and under dc electric field up to 45 V/mu m in view of their application in tunable film bulk acoustic wave resonators. The observed relatively high permittivity 130 without remarkable frequency dispersion is explained by contribution of the domain wall vibrations. It is shown that the substrate induced strain and Maxwell-Wagner contributions are negligible. The measured dielectric response allows estimation of the BiFeO3 sound velocity and acoustic impedance as 3100 m/s and 26 . 10(6) kg/m(2)s, respectively.