Negative and positive photodielectric effects in quantum paraelectric BaFe12O19 single crystals

Abstract

The effects of light illumination on dielectric properties were investigated in ferrimagnetic quantum paraelectric BaFe₁₂O₁₉ single crystals. The enhancement and reduction of dielectric constants under light illumination, i.e., positive and negative photodielectric (PD) effects, were found in BaFe₁₂O₁₉. The high-temperature positive PD effect depends significantly on the frequency and temperature, which can be ascribed to the photo-excitation accelerated electron hopping process between Fe²⁺ and Fe³⁺. The low-temperature negative PD effect is nearly frequency-independent and is associated with non-polar tendency of the FeO₅ bipyramids induced by photo-excited carriers. These findings could suggest a promising route to generate large and frequency-independent PD effects for application in photo-sensing devices.