Enhancing reversible entropy change of all-d-metal Ni37.5Co12.5Mn35Ti15 alloy by multiple external fields

Abstract The multiple external fields have been introduced to enhance the reversible entropy change of all-d-metal Ni37.5Co12.5Mn35Ti15 alloy. Our studies reveal that the reversible entropy change can be largely increased from 8.9 J kg−1K−1 to 24.1 J kg−1K−1 for a magnetic field change of 0.01 T to 5 T. The combined investigations of structural transition by transmission electron microscopy and magneto-strain reveal a strong coupling between magnetism and volume in the alloy, due to which, the magneto-structural transition temperature of Ni37.5Co12.5Mn35Ti15 decreases with the magnetic field by a rate of -1.4K T−1, and increases with the hydrostatic pressure by a rate +5K kbar−1, thus providing the condition for the promotion of reversible entropy change under multiple fields cycling.