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

Abstract

Perpendicular magnetic anisotropy and coercive fields (Hc) 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 Hc extending from 10 to 7.5 kOe for three Mn4N films grown at a substrate temperature (Tsub) 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 Tsub. This indicates that Hc of the Mn4N film with the same S is sensitive to the variation in dislocations, D and ε. Tunable Hc of this type can be effectively applied in magnetic and spintronic devices using ferrimagnetic Mn4N films, because Hc is an important determinant of the thermal stability of magnetization and working power consumption.