In the present work, high-energy milling under two different atmospheres was applied to the intermetallic compound and to the chemical elemental powders of Er and Fe with stoichiometric composition. Sample A is the compound milled under Ar, sample B the compound milled under and sample C the elemental powders milled under atmosphere. X-ray diffraction (XRD) and Mössbauer spectroscopy (MS) results of the samples A and B show a segregation process with increase of the milling time. Under atmosphere, the initial compound was nearly dissociated with 50 h of milling, while with Ar atmosphere the segregation process was completed with 100 h of milling. From the analysis of the XRD and MS results, it was possible to observe the appearance of other phases at intermediate milling times, in both samples A and B. One phase was associated with an amorphous alloy with a magnetic ordering temperature, obtained by AC magnetic susceptibility, at about 190 K, a second phase was attributed to nanocrystallites of and a third one associated with an fcc Er high-pressure phase stabilized by N atoms. In the case of sample B, for milling times longer than 400 h, XRD and MS results indicate the presence of an Fe-Er-N disordered alloy, with magnetic ordering temperature above room temperature. The XRD and MS results of sample C show the formation of an amorphous phase, with about 87% of MS relative area in this phase at 68 h of milling.