LaMnO3 Revisited

We revisit the prototypical Jahn-Teller distorted perovskite LaMnO3. We
introduce a new simple notation concatenating local and cooperative aspects of
Jahn-Teller distortions in perovskites on the basis of irreducible representations
of phonon modes and lattice strains. This description gives a rigorous
orthogonal basis to study the interlock between individual lattice distortions,
strains, electronic properties and magnetic orderings. By sampling the potential
energy surface of the close competing ferromagnetic and A-type
antiferromagnetic orders, we show that the main parameter promoting one
magnetic potential energy surface with respect to the other is the value of
tetragonal strain. On the basis of this knowledge, we reinvestigate the epitaxial
strain phase diagram of thin films and clarify the origin of the intriguing
ferromagnetic insulating phase found in LaMnO 3 films grown on SrTiO3.
Finally we discuss the possibility of designing multiferroic RMnO 3-based
superlattices including strong ferromagnetism from appropriate combination of
epitaxial strain and cationic ordering.