Structural, magnetic and magnetocaloric effect studies of Ni42.5(Fe, Co, Ni, Cu)0.5Mn46Sn11 Heusler alloys

We investigated the structural and magnetic properties of Ni42.5(Fe, Co, Ni, Cu)0.5Mn46Sn11 alloys fabricated by arc melting. Substitution of Ni by Fe, Co and Cu causes lattice expansions consistent with increasing atomic sizes. The zero-field cooled and field cooled results show second-order magnetic transition at the high-temperature austenite phase to a first-order magnetic transition in the low-temperature martensite phase. The substitution of Ni by Fe and Co increases the austenite Curie temperature TCA from 282 K to 289 K and 294 K respectively while Cu reduces it to 278 K. The martensitic transition temperature TM increased from 221 K to 241 K for Fe substitution and decreased to 210 K and 209 K for Co and Cu respectively. The coercive field HC increased significantly from 457 Oe for Ni at 100 K to 729 Oe for Co at 80 K. The increase to 763 Oe for Fe and 769 Oe for Cu occurred at the same temperature of 40 K. We attribute such increases to domain wall pinning effects due to the inclusions of Fe, Co...