Dependence of exchange bias energy on spin projections at (La,Ca)MnO3 ferromagnetic/antiferromagnetic interfaces

Strained epitaxial bilayers and multilayers consisting of La1−xCaxMnO3 ferromagnetic (FM) layers (x=0.33, 0.4) and La0.33Ca0.67MnO3 antiferromagnetic (AF) layers were grown on (001)LaAlO3 to study the evolution of exchange coupling interactions. The epitaxy was revealed by conventional and high resolution electron microscopy. An out-of-plane lattice expansion is observed mainly on the FM layers that induces a spontaneous magnetization component normal to the film plane. Field-cooling experiments with the applied field parallel and perpendicular to the film plane exhibit loop-shifts (exchange biasing) and enhanced coercivities that depend on the spin projections at the AF/FM interfaces.