Giant irreversibility of the inverse magnetocaloric effect in the Ni₄₇Mn₄₀Sn_12.5Cu_0.5 Heusler alloy

Direct studies of the adiabatic temperature change (Delta T-ad) in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni47Mn40Sn12.5Cu0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254-283 K temperature range as well as a second order phase transition near the Curie temperature T-C = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value Delta T-ad = -12 K in 20 T at the initial temperature T-0 = 275 K. The irreversible part of the MCE reached Delta T-ir = -10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems.