EELS spectra were acquired with energy dispersion of 0.05 eV and 2 mm spectrometer aperture. The Dual-EELS function of the GIF-QuantumER TM spectrometer, allowing the simultaneous acquisition of two different energy ranges, was used to record simultaneously Zero-Loss peak (0.0001 s exposition time, 10 frames) and Fe-L2,3 coreregion in order to minimize the uncertainty on the energy shift of the Fe-L2,3 edges. Insitu TEM annealing experiments were performed with a JEOL JEM 2100HT transmission electron microscope at a temperature of 300 ºC using a Gatan 652 double-tilt heating holder. For in situ annealing TEM and (S)TEM observations, the samples were prepared by crushing in an agate mortar, ultrasonically dispersing the crushed powders in n-butanol and finally transferring them to carbon-coated copper or molybdenum grids.