Optically driven conductivity and magnetoresistance in a manganite-based tunnel structure

In the multilayer structure, La(0.7)Sr(0.3)MnO(3)/depleted manganite layer/MnSi, the photovoltaic effect has been discovered. The depleted manganite layer in the structure is dielectric and serves as a potential barrier between the ferromagnetic conducting La(0.7)Sr(0.3)MnO(3) and MnSi layers by the formation of a magnetic tunnel junction. The photoinduced changes in the transport properties of the magnetic tunnel structure have been observed in the current-in-plane geometry. The changes are reversible and saturate at radiation power densities over 30 mW cm(-2). The photovoltaic effect has a threshold character: it reveals only at h nu > 1.17 eV. Most likely, the effect of optical radiation is related to the formation of electron-hole pairs due to interband absorption of light in the dielectric layer. A photocurrent through the tunnel junctions separating the conducting layers causes a redistribution of the current channels between the conducting layers, which influences the conductivity and the magnetoresistance of the structure.