Direct pulsed-field magnetocaloric dynamics of a single melt-spun Ni–Co–Mn–Ti ribbon

The magnetocaloric response of melt-spun all-d-metal Ni$_{36}$Co$_{14}$Mn$_{37}$Ti$_{13}$ ribbon samples was investigated with particular emphasis on the direct pulsed-field determination of the adiabatic temperature change, ΔT$_{ad}$. The ribbons exhibit an A2-like disordered cubic parent phase and a first-order martensitic transformation near room
temperature with a thermal hysteresis of about 34 K. Microstructural analysis reveals a dual-grain morphology, which contributes to the broadening of the transformation interval. The maximum isothermal entropy change, ΔSiso, reaches 20.1 J/kg K under 5 T, while the temperature-averaged entropy change (TEC) yields TEC(5) = 17.5 J/kg, indicating promising practical cooling capability. A central result of this work is the direct determination of ΔT$_{ad}$ in melt-spun ribbons with an active mass of only ~1 mg using pulsed magnetic fields up to 20 T. For the direct ΔTad measurements, a free-standing sample configuration was employed to reduce parasitic heat exchange and better approach quasi-adiabatic conditions. The largest net cooling after a complete field-on/field-off cycle reaches approximately 5 K at 281 K under a 10 T pulse, whereas increasing the field to 20 T does not enhance the overall cooling. ... mehrMoreover, the temperature decrease evolves with different slopes for different pulse
amplitudes, suggesting that both the extent of the field-induced transformation and non-equilibrium transformation dynamics influence the measured response. These results demonstrate the feasibility of direct pulsed-field magnetocaloric measurements on extremely low-mass ribbons and provide insight into their cooling response under high pulsed magnetic fields.