Fig. 2.

RIXS study of the distinct magnon modes of the bulk-like and interfacial CuO₂ layers. A) Sketch of the RIXS and polarimetry experiments indicating the measurement geometry. B) Scheme of the magnetic order and exchange interaction of the Cu- and Mn-spins in the vicinity of the cuprate/manganite interface. C) Reciprocal lattice vectors of the structural (green dots) and the magnetic (red dots) orders with the corresponding first BZ shown by dotted lines. D and E) Representative RIXS spectra at [$0.3\times A$*] showing the two magnon modes M1 (blue shading) and M2 (red shading) along with phonons (gray shading) and the elastic line (gray line) at the bulk-like Cu resonance of 931 eV and the interfacial Cu resonance of $930.5$ eV, respectively. The spectra are normalized with respect to the area of the dd-excitations beyond $-$1 eV (not shown). F) Corresponding RIXS–polarimetry spectra at [$0.3\times A$*] and 931 eV showing that the M1 and M2 modes are predominantly from spin-flip scattering and thus of magnetic origin. The error bars have been calculated as described in Section S3.2 (40).