Multiferroic behavior of disordered bismuth-substituted zinc ferrite

In this study, we reported the multiferroic behavior of disordered bismuth-substituted zinc ferrite. Bi:ZnFe2O4 films were deposited by using the RF-magnetron sputtering method. As-deposited films exhibited a ferromagnetic hysteresis and a large Faraday rotation angle in the short wavelength range (∼400 nm): a saturation magnetization of 120 G and the Faraday rotation angle of −1.2 deg/μm were observed. Ferroelectric hysteresis was measured using the Sawyer-Tower method. Dielectric constant of Bi:ZnFe2O4 was measured with a LCR meter in a frequency range from 120 Hz to 100 kHz. For 120 Hz, the dielectric constant of 800 was observed at room temperature. By contrast, the dielectric constant of disordered zinc ferrite was 5.5 at 120 Hz. Our studies showed that bismuth substitution in ZnFe2O4 enhanced the dielectric constant drastically. Furthermore, in the films, voltage-induced alteration of the magneto-optic Kerr rotation angle was identified.