High Strength and Low Coercivity of Cobalt with Three-Dimensional Nanoscale Stacking Faults.

Liu, Yue; Song, Jian; Liu, Guisen; Chen, Jinsong; Wang, Chaoxiang; Wang, Haiyan; Wang, Jian; Zhang, Xinghang · Nano Lett · 2021

basic_science · Level V

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Abstract

Lower coercivity (<i>H</i><sub>C</sub>) and magnetic anisotropy (<i>K</i><sub>1</sub>) 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 <i>H</i><sub>C</sub> and <i>K</i><sub>1</sub> 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 <i>H</i><sub>C</sub> 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.