Wide modulation of coercive fields in Mn₄N ferrimagnetic thin films caused dominantly by dislocation microstructures

Perpendicular magnetic anisotropy and coercive fields (H_c) are governed by the degree of order of N (S) in ferrimagnetic Mn₄N thin films. However, in this study, we observed non-negligible modulation of H_c extending from 10 to 7.5 kOe for three Mn₄N films grown at a substrate temperature (T_sub) in the range of 400–500 °C, even with identical S, which has not been discussed to date. The possible mechanisms for this phenomenon were explored by transport properties and fine structural analysis. The results indicated that longitudinal resistivity and anomalous Hall resistivity remain unchanged for three Mn₄N films. Conversely, the number of dislocations and in-plane grain size (D) increased, whereas the residual strain (ε) decreased with increasing T_sub. This indicates that H_c of the Mn₄N film with the same S is sensitive to the variation in dislocations, D and ε. Tunable H_c of this type can be effectively applied in magnetic and spintronic devices using ferrimagnetic Mn₄N films, because H_c is an important determinant of the thermal stability of magnetization and working power consumption.