Enhancing reversible entropy change of all-d-metal Ni_37.5Co_12.5Mn₃₅Ti₁₅ alloy by multiple external fields

The multiple external fields have been introduced to enhance the reversible entropy change of all-d-metal Ni_37.5Co_12.5Mn₃₅Ti₁₅ 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 Ni_37.5Co_12.5Mn₃₅Ti₁₅ 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.