The magnetocaloric performance in pure and mixed magnetic phase CoMnSi

Abstract

Here we study the influence of sample preparation on the magnetocaloric properties of CoMnSi. Slow cooling from the high temperature hexagonal phase of the melt to the room temperature orthorhombic phase encourages the formation of a homogeneous material with large entropy changes when the system undergoes a coincident first order structural and (meta)magnetic transition. Samples that were quenched directly after annealing show a compressed a axis lattice parameter. Hall probe imaging indicates that the quenched sample has spatially inhomogeneous magnetic properties, which we attribute to strain because within error neither x-ray diffraction nor energy dispersive x-ray analysis indicates a second compositional phase. Calorimetric methods and global magnetization are used to examine the entropy changes of the pure and mixed magnetic phase compounds and we make a direct comparison of these materials in terms of their refrigerant capacity.