Interplay of lattice strain and spin-polarization in ferromagnetic–insulator–ferromagnetic thin films: La0.7Ca0.3MnO3/LaAlO3/La0.7Sr0.3MnO3

Epitaxial thin films of ferromagnet/insulator/ferromagnet layers (La0.7Ca0.3MnO3/LaAlO3/La0.7Sr0.3MnO3) of different thickness were fabricated by pulsed laser deposition. Microstructural analysis shows island growth on the thicker film surface. dc magnetization study demonstrates the strong signature of domain wall freezing for the composite film. An interesting feature is a cusp/upturn in field-cooled curve in the composite film-1, much below TB, the blocking temperature. The low temperature cusp disappears in the composite film-2. We suggest that a quasistable charge ordering via spin localization at low temperature, especially for film-1, is the origin of this feature.