  A variety of emergent phenomena has been enabled by interface engineering in
the complex oxides heterostructures. While extensive attention has been
attracted to LaMnO3 (LMO) thin films for observing the control of
functionalities at its interface with substrate, the nature of the magnetic
phases in the thin film is, however,controversial. Here, it is reported that
the ferromagnetism in 2 and 5 unit cells thick LMO films epitaxially deposited
(001)-SrTiO3 substrates ferromagnetic/ferromagnetic coupling in 8 and
10-unit-cell ones, and a striking ferromagnetic/antiferromagnetic pinning
effect with apparent positive exchange bias in 15 and 20-unit-cell ones are
observed. This novel phenomenon in both 15 and 20-unit-cell films indicates a
coexistence of three magnetic orderings in a single LMO film.The
high-resolution scanning transmission electron microscopy suggests a P21/n to
Pbnm symmetry transition from interface to surface, with the spatial
stratification of MnO6 octahedral morphology, corresponding to different
magnetic orderings. These results should shed some new lights on manipulating
the functionality of oxides by interface engineering.
