Magnetooptical response to tunnel magnetoresistance in manganite films with a variant structure

The optical, magnetooptical, electrical, and magnetic properties of La0.67Ba0.33MnO3 films grown on the SrTiO3 and ZrO2(Y2O3) substrates have been studied. The temperature and magnetic field dependences of magnetotransmission of light in the La0.67Ba0.33MnO3/ZrO2(Y2O3) film with a variant structure exhibit features which can be attributed to an optical response to tunnel magnetoresistance - tunnel magnetotransmission. Unlike the optical response to colossal magnetoresistance, existing near the Curie temperature only, the tunnel magnetotransmission increases at T → 0 K, has a complex hysteresis behavior with the change of sign of the effect, and saturates in magnetic fields above 1 kOe. The observed tunnel magnetotransmission has been interpreted within the magnetorefractive effect theory developed for granular films.