Magnetoreflection and Kerr effect in La$_{2/3}$Ba$_{1/3}$MnO$_{3}$ films posessing a variant structure

A correlation was found between the magnetoreflection of natural light and tunneling magnetoresistance in La$_{2/3}$Ba$_{1/3}$MnO$_{3}$ films with a variant structure grown on ZrO$_{2}$(Y$_{2}$O$_{3}$) substrates. It was shown that the magnetoreflection as well as the colossal magnetoresistance, is maximum in the region of magnetic ordering near room temperature ($T_C\sim$ 295 K) of the films. The magnetoreflection spectra of a La$_{2/3}$Ba$_{1/3}$MnO$_{3}$ film with the variant structure are formed by the same mechanisms as in the case of films without the variant structure and can be described in terms of the theory of the magnetorefractive effect. The field and temperature dependences of magnetoreflection demonstrate the presence of an additional low-temperature contribution to the reflection of the La$_{2/3}$Ba$_{1/3}$MnO$_{3}$ film due to tunneling of spin-polarized electrons through the boundaries of structural domains.