Intriguing photo-control of exchange bias in BiFeO3/La2/3Sr1/3MnO3 thin films on SrTiO3 substrates

To date, electric fields have been widely used to control the magnetic properties of BiFeO3-based antiferromagnet/ferromagnet heterostructures through application of an exchange bias. To extend the applicability of exchange bias, however, an alternative mechanism to electric fields is required. Here, we report the photo-control of exchange bias in BiFeO3/La2/3Sr1/3MnO3 thin films on an SrTiO3 substrate. Through an ex situ pulsed laser deposition technique, we successfully synthesized epitaxial BiFeO3/La2/3Sr1/3MnO3 thin films on SrTiO3 substrates. By measuring magnetoresistance under light illumination, we investigated the effect of light illumination on resistance, exchange bias, and coercive field in BiFeO3/La2/3Sr1/3MnO3 thin films. After illumination of red and blue lights, the exchange bias was sharply reduced compared to that measured in the dark. With increasing light intensity, the exchange bias under red and blue lights initially decreased to zero and then appeared again. It is possible to reasonably explain these behaviors by considering photo-injection from SrTiO3 and the photo-conductivity of La2/3Sr1/3MnO3. This study may provide a fundamental understanding of the mechanism underlying photo-controlled exchange bias, which is significant for the development of new functional spintronic devices.