Photoinduced Resistivity Change Due to Spin-Disorder in a Manganite Film

Photoinduced resistivity change (ΔR/R) in a La0.6Sr0.4MnO3 film has been investigated with variation of the excitation energy E exc (1.88–3.20 eV) and temperature (290–400 K). The magnitude of the photoinduced resistivity change steeply decreases with increasing temperature beyond T c∼315 K. In addition, we have found that the photoinduced signal is enhanced when the down-spin e g carriers are excited. Based on these experimental findings, we have ascribed the positive ΔR/R signal to the photoinduced spin disorder in the ferromagnetic metallic (FM) state.