| Sumario: | 7 pages. -- Figure S1. a) X-ray diffraction around STO(001). Finite size fringes indicate high-crystalline quality for all the LNMO films. Data for different films is shifted for increased visibility. b) Topography of a 5-uc-thick LNMO film. Step-and-terrace morphology is inherited by the TiO2-terminated STO substrate. c) Reciprocal space map around STO(103) indicates that a 90 uc (~ 35 nm) LNMO film is epitaxially strained to the substrate. -- Figure S2. a) Mn L3,2-edges XMCD spectra. b) Ni L3,2-edges XMCD spectra. -- Figure S3. a) XAS of Mn L3,2-edges for 5-uc-thick LNMO films subjected to different epitaxial strain conditions. The six different perovskite oxide substrates: LaAlO3 (LAO), NdGaO3 (NGO), LSAT, LaGaO3 (LGO), STO, and DyScO3 (DSO), exert a nominal strain of -2.1%, -0.5%, -0.2%, +0.4%, +0.7%, and +1.8% respectively. The LNMO heterostructure with the highest Mn3+ content is the one grown on STO, followed by the one on LSAT. Overall, the other heterostructures have similar spectra despite the very different strain conditions ranging from highly compressive to highly tensile. Still, signatures of Mn3+ can be observed in tensile-strained LNMO films grown on LGO and DSO. Data is collected at 300 K. b) Same data as in a) but spectra are vertically shifted for increased visibility. Reference lines for L3,2-edges maxima are also shown. c) Sketch of interfacial stacking sequence of LNMO//LSAT. The nominal ionic charge of each layer is indicated on the left. A polar discontinuity at the interface between film and substrate is present, albeit weaker when compared to LNMO//STO (Figure 2c). d) Sketch of interfacial stacking sequence of LNMO//LGO. -- Figure S4. Projected DOS for the Ni0.5Mn0.5O2 layer adjacent to the LNMO//STO (top) and LNMO//LGO (bottom) interface. -- Figure S5. Projected layer-resolved DOS for VO placed in the a) first, b) eleventh, c) twelfth and d) thirteenth layer from the surface of the LNMO//STO heterostructure. -- Figure S6. a) HAADF-STEM survey image of a 13 uc LNMO//STO film and corresponding atomic-resolution EDX elemental maps calculated from the EDX spectrum image using the Sr Kα, Ti Kα, La Lα, Mn Kα and Ni Kα lines. -- Figure S7. At neutral charge the rock-salt configuration (a) is the most stable while the row configuration (c) is the least stable. On the other hand, after adding an extra electron to the system, the column configuration (b) is the most stable. -- Figure S8. The DOS are shifted by the vacuum level determined from (001)pc surface calculations (the work functions for LNMO, LNO and LAO are 4.26, 4.71 and 5.49 eV respectively). -- Figure S9. a) XAS of Mn L3,2-edges for 5- and 10-uc-thick LNMO//STO shows different Mn3+ content as already evidenced in Figure 2a. LNO capping results in a Mn4+-like spectra while the LAO capping is characterized by the persistent presence of Mn3+. Data collected at 20 K. b) XAS of Mn L3,2-edges for 5- and 9-uc-thck LNMO//LSAT shows a larger Mn3+ content for reduced LNMO thickness, similar to what already observed at the LNMO//STO heterostructure. -- Figure S10. Normalized SQUID magnetization vs temperature of a LNO/LNMO(2uc)//STO heterostructure measured in a magnetic field of 0.5 T (gray line).
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