Interfacial Control of Ferromagnetism in Ultrathin La_0.67Ca_0.33MnO₃ Sandwiched between CaRu_1–xTi_xO₃ (x = 0–0.8) Epilayers

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 La 0.67 Ca 0.33 MnO 3 (LCMO) layer sandwiched between CaRu 1– x Ti x O 3 [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- e g ( x 2 – y 2 ) 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.