For the measurement, the samples were mixed with boron nitride, placed in polycarbonate hole plates with a thickness of 1 mm and sealed with a polyimide tape (Kapton) on both sides. Before collecting the sample spectra, a cobalt and nickel foils were used as references for the respective K edges. The relative energies of the spectra were calibrated against the first inflection point from the first derivative of the cobalt/nickel metal absorption edge.