High maximum energy product in SmCo/Fe multilayers: a micromagnetic simulation of layer sequencing and thickness optimization

In this work, we investigated magnetic SmCo/Fe multilayers with two types of layer alternation (from<i>n</i>= 2 to<i>n</i>= 17 layers with either soft or hard layers at the edges) to obtain structures with the highest value of maximum energy product (<i>BH</i>)_maxusing the micromagnetic simulation package MuMax3. The highest (<i>BH</i>)_maxvalue of 85.6 MGOe was achieved for [SmCo(0.4 nm)/Fe(2.8 nm)]₂/SmCo(0.6 nm)/Fe(2.8 nm)/SmCo(0.6 nm)/Fe(3.2 nm)/SmCo(0.6 nm)/Fe(2.8 nm)/SmCo(0.6 nm)/[Fe(2.8 nm)/SmCo(0.4 nm)]₂structure with hard outer layers due to the absence of free soft surfaces. A slightly lower value of 85 MGOe was obtained for the optimal structure of the other type (with Fe layers at the edges). These enhancements were attributed to a transition from domain wall pinning to nucleation mechanism and a simultaneous increase in the average saturation magnetization. Our results provide a clear design strategy for high-performance exchange-spring magnets with reduced hard magnetic phase content.