Tailored martensitic transformation and enhanced magnetocaloric effect in all-d-metal Ni₃₅Co₁₅Mn₃₃Fe₂Ti₁₅ alloy ribbons

The crystal structure, martensitic transformation and magnetocaloric effect have been studied in all-d-metal Ni_35Co_15Mn_33Fe_2Ti_15 alloy ribbons with different wheel speeds (15 m/s (S15), 30 m/s (S30), and 45 m/s (S45)). All three ribbons crystalize in B2-ordered structure at room temperature with crystal constants of 5.893(2) Å, 5.898(4) Å, and 5.898(6) Å, respectively. With the increase of wheel speed, the martensitic transformation temperature decreases from 230 K to 210 K, the Curie temperature increases slightly from 371 K to 378 K. At the same time, magnetic entropy change (\Delta S_\rm m) is also enhanced, as well as refrigeration capacity (RC). The maximum \Delta S_\rm m of 15.6(39.7) J/kg\cdotK and RC of 85.5 (212.7) J/kg under \Delta H = 20 (50) kOe (1 \rm Oe=79.5775 A\cdotm^-1) appear in S45. The results indicate that the ribbons could be the candidate for solid-state magnetic refrigeration materials.