High Strength and Low Coercivity of Cobalt with Three-Dimensional Nanoscale Stacking Faults
Yue Liu, Jian Song, Guisen Liu, Jinsong Chen, Chaoxiang Wang, Haiyan Wang, Jian Wang, X. Zhang
Abstract
Lower coercivity (HC) and magnetic anisotropy (K1) coupled with high mechanical strength are essential properties for Co-based soft magnetic thin films; however, the strength-coercivity trade-off limits their development. Co with face centered cubic structure (fcc) exhibits lower HC and K1 than its grand hexagonal close packed structure (hcp); however, metastable fcc-phase Co is hard to stabilize. Here, by using Cu (100) seed layer, we synthesized micron-thick fcc Co films with self-formed three-dimensional nanoscale stacking faults (3D-nSFs) that could achieve high strengths without sacrificing soft magnetic properties. The 3D-nSFs, induced by the Co/Cu interface, could not only stabilize the metastable fcc Co to yield lower HC but also impede dislocation motion to strengthen Co films. More importantly, we successfully tailored the density of 3D-nSFs and confirmed a large variation in magnetic coercivity (by 100%) and indentation hardness (by 25%). This work provides a new strategy for integrated performance optimization by interface design and strain engineering.