Supplementary material

supplementary material for cross-sectional STEM images, the field-dependent ∆R(t)/R0 time series at 10 K of the Au/LSMO films, representative fitting, a zoom-in view of the high-density Au/LSMO curve in Fig. 2b, extracted fitting parameters of field- dependent ∆θK(t) curves for all the samples, and the schematic layout for field dependent femtosecond transient optical spectroscopy measurements.