Controlling functionalities
in oxide heterostructures remains challenging for the rather complex
interfacial interactions. Here, by modifying the interface properties
with chemical doping, we achieve a nontrivial control over the ferromagnetism
in ultrathin La0.67Ca0.33MnO3 (LCMO)
layer sandwiched between CaRu1–xTixO3 [CRTO(x)] epilayers. The Ti doping suppresses the interfacial electron transfer
from CRTO(x) to LCMO side; as a result, a steadily
decreased Curie temperature with increasing x, from
262 K at x = 0 to 186 K at x = 0.8,
is observed for the structures with LCMO fixed at 3.2 nm. Moreover,
for more insulating CRTO(x ≥ 0.5), the electron
confinement induces an interfacial Mn-eg(x2–y2) orbital order in LCMO which further attenuates the ferromagnetism.
Also, in order to characterize the heterointerfaces, for the first
time the doping- and thickness-dependent metal–insulator transitions
in CRTO(x) films are examined. Our results demonstrate
that the LCMO/CRTO(x) heterostructure could be a
model system for investigating the interfacial multiple interactions
in correlated oxides.