Magnetic and structural phase transitions in epitaxial thin films of Manganites

Understanding the magnetic properties of complex materials near interfaces is important for the development of functional nanostructures and devices. Epitaxial LaMnO$_{3}$ films were grown on SrTiO$_{3}$ substrates. Recent work on such thin-film samples has shown that ``interface doping'' can induce magnetism at interfaces. Our work on LaMnO$_{3}$/SrTiO$_{3}$ interfaces has shown that the nature of the interface determines its magnetic structure - with the MnO$_{2}$-SrO interface showing a different magnetization than the LaO-TiO$_{2}$ interface. To investigate interfacial structures, we used polarized neutron reflectometry with off-specular scattering. Our results give evidence of reversible temperature- and field- dependent structural changes in LaMnO$_{3}$ film which undergo a phase transition. We determined that a structural phase transition in SrTiO$_{3}$ and the misfit strain trigger appearance of twins to reduce stresses and to adjust lattice mismatch between the film and the substrate. We show that a laterally correlated superstructure appear due to interaction of structural modifications with the magnetization the film