Electric Field Biased Faraday Effect in Cr-doped BiFeO_3 Thin Film

摘要

Multiferroics, materials which possess multiple ferroic orders, have seen a revival of interest in recent years as the need for multifunctional and multitunable devices has increased. These particular materials are of interest due to the potential to control and tune devices by both electric and magnetic fields. Examining how an external electric field alters the magneto-optic response of the well-known multiferroic, BiFeO_3 (BFO), could provide useful insight into how these multiferroics would function in optical devices. The Faraday rotation of a 10% Cr-doped BFO (111) thin film on an MgO substrate was measured for three conditions using an ac magnetic field technique: no biasing electric field, a positive 2 kV/m electric field, and a negative 2 kV/m electric field. The Verdet constant for these three conditions at an optical wavelength of 632.8 nm was 20.48 ± 1.96 °/kOe-cm, 21.25 ± 3.33 °/kOe-cm, and 2.01 ± 0.5 °/kOe-cm respectively. These results demonstrate the possibility to manipulate the magneto-optic response of the thin film with an external dc electric field. Future work to both overcome the deficiencies exhibited by BFO and investigate how precisely the magneto-optic response can be controlled by an external field is presented and discussed.