Large photoresistance and photoinduced magnetoresistance in La_0.67Ca_0.33MnO₃ thin film on silicon substrate

Abstract

The effects of light illumination and magnetic field on the electrical transport properties of La0.67Ca0.33MnO3 thin film on a silicon substrate have been studied in detail. Large value of colossal magnetoresistance has been observed under an applied magnetic field in the whole temperature range below 150 K which is related to the presence of both antiferromagnetic and ferromagnetic phase in the sample. A significant amount of resistance drop is caused by lightillumination even at extremely low light intensities, ~ -22% with light of 0.3 μW/cm2 intensityand ~ -42 % with 6.2 μW/cm2 intensity at 600 nm wavelength. There has been a notable rise in the photoinduced magnetoresistance value, specifically, a significant decrease in resistance occurs in simultaneous presence of magnetic field and light. For 1 T applied magnetic field, -MR% rises from -33 % in dark to -58 % under light illumination at 150 K i.e. ∆MR % is 25 %. As the strength of the magnetic field increases, ∆MR % decreases, suggesting that the magnetoresistive photoinduced phenomenon is more pronounced in the presence of mix phases in the sample. This combined enhanced magnetoresistive photoinduced phenomenon is explained by the interaction of photogenerated charge carriers in the sample and applied magnetic field.