Interface Orbital/Charge Reconstruction and Its Effect on Spin Orientation for (110)-La_2/3Sr_1/3MnO₃ Layer Sandwiched by LaCoO₃ Films

Here we made the first attempt to reveal the effect of orbital/charge reconstruction associated with interface engineering on spin degree of freedom. We took tensely strained (110)-LaCoO₃/La_2/3Sr_1/3MnO₃/LaCoO₃ trilayers as specimens, focusing on orbital reconstruction and accompanied effects. The most remarkable finding is the reordering of the energy levels of Mn-3d orbitals: the low-lying orbital becomes d_x2-y2 for sandwiched La_2/3Sr_1/3MnO₃ rather than d_3z2-r2 as expected for a bare La_2/3Sr_1/3MnO₃ film. Interlayer charge transfer via d_x2-y2 orbitals is further detected, which is the driving force for orbital reconstruction. Due to spin-orbit coupling, the charge/orbital reconstruction produces a chain effect on spin degree of freedom of the La_2/3Sr_1/3MnO₃ layer, resulting in a dramatic spin reorientation by 90° in film plane. The present work vividly demonstrates how to tune macroscopic properties of correlated oxides via the mutual coupling between different degrees of freedom.