Effect of Co on spinodal decomposition and magnetic properties in Fe(67_X)Cr31CoXSi2 (X=9, 14, 19, 24) medium entropy alloys

We synthesized four Fe(67_X)Cr31CoXSi2 (X = 9, 14, 19, and 24 at.%) medium-entropy alloys and investigated the effect of Co on the connection between magnetic properties and spinodal structure. When the value of X was increased from 9 to 14 at.%, both the volume fraction of alpha 1 phase and the composition difference between alpha 1 and alpha 2 phases increased, leading to an increase in coercivity. This increase also resulted in an increase in the size of alpha 1 phase, leading to a decrease in remanence. When the value of X was increased beyond 14 at.%, both coercivity and remanence were significantly enhanced, even though the volume fraction of the alpha 1 phase remained unchanged. We attribute this enhancement to (1) intensification of the composition fluctuation in the spinodal structure, (2) increase in lattice misfits, and (3) refinement of the alpha 1 phase. Our results will be valuable in future magnet design.