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 n = 2 to n = 17 layers with either soft or hard layers at the edges) to obtain structures with the highest value of maximum energy product (BH)max using the micromagnetic simulation package MuMax3. The highest (BH)max value of 85.6 MGOe was achieved for [SmCo(0.4nm)/Fe(2.8nm)]2/SmCo(0.6nm)/Fe(2.8nm)/SmCo(0.6nm)/Fe(3.2nm)/SmCo(0.6nm)/Fe(2.8nm)/SmCo(0.6nm)/[Fe(2.8nm)/SmCo(0.4nm)]2structurewith 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.