“…5,13 Prior to Raman spectroscopy, the structural, magnetic, and chemical properties of the samples are extensively investigated 5 and in particular the crystalline structure is analysed by synchrotron high-resolution x-ray diffraction and high-resolution transmission electron microscopy, showing that all samples are single-crystalline and do not include secondary phases. Furthermore, synchrotron x-ray absorption fine structure (EXAFS) studies demonstrate that at least 95% of the Mn ions substitutes Ga cations, 14 and we have reported that in the case of Mn-Mg codoping, both Mn and Mg occupy Ga substitutional sites, and Mg tends to stay close to Mn, separated by one N atom, to form Mn-Mg k cation complexes, where k is the number of Mg ions in the first cation shell of a single Mn. 5 The Mn and Mg concentrations x Mn and x Mg are extracted from secondary ion mass spectroscopy (SIMS) and lie between 0% and 1%.…”