Modulation of Electric Current on Photoinduced Spin-Disorder in a Manganite Film

We investigate the photoinduced resistance change (Δ R/R) in a La_0.6Sr_0.4MnO₃ film (T_c\sim 325K) at different applied dc currents I (0.1--2.0mA) at 295K. At I = 0.1mA, we have found a significant photoinduced ΔR/R～17% under photo-irradiation at excitation energy E_exc = 3.05eV and pump power P_pump = 2.5mJ/cm², which has been ascribed to the photo-excited down-spin e_g carriers and hence the spin-disorder in the ferromagnetic metallic state. With increasing applied electric current to 2.0mA, the magnitude of the photoinduced ΔR/R is reduced to 3%, which may be attributed to current-induced ordering of the localized spins.