In this investigation, the effect of deformation on magnetic properties at low temperatures of FeCr_18.2Mn_18.9–0.96C + N high interstitial steel was studied. Tensile tests were carried out at room temperature and interrupted at 10, 20, and 30 pct deformation. Magnetic measurements were performed through the vibrating sample magnetometry (VSM) technique from 50 K to 370 K. Microstructural, morphological, and crystalline structural analyses by means of XRD and SEM showed that the material consisted of a homogenous and stable austenitic structure with no presence of α-martensite or ε-martensite. Twinning and dislocation cells are suggested as main deformation mechanisms. The material exhibits a paramagnetic–antiferromagnetic (T_Néel) transition below 235 K. The Néel temperature of the material tends to increase due to the deformation. A decrease of the magnetization and magnetic susceptibility for the deformed material was measured. Ab initio calculations were performed and showed that the FCC phase is more stable when carbon and nitrogen are added as interstitial elements compared with the free C + N system, additionally, the critical transition temperature was calculated, with a value in agreement with the experimental data. An influence of the magnetic contribution on the SFE was established, being in the order of 5 mJ/m².